Nothing is more disruptive than a computer that reboots itself in the middle of your work. One moment you are writing an email or playing a game, and the next you are staring at the Windows logo as everything you had open vanishes. Learning how to fix a PC that randomly restarts starts with understanding one thing: the restarts are a symptom, not the problem. Something — heat, unstable power, a faulty driver, or a dying hardware component — is triggering them, and your job is to find out what.
This guide walks you through the diagnosis in a logical order, from the fastest checks to the deeper hardware tests. You do not need expensive tools or a technician’s bench; most of these steps need nothing more than your PC and a little patience. Where a related Paxi guide covers a step in more depth, you will find a link to it.
Quick Answer
A PC that randomly restarts usually has one of these causes: overheating CPU or GPU, a failing or under-powered power supply unit (PSU), faulty RAM, outdated or corrupt device drivers, or a recent Windows update that went wrong. Check your CPU temperatures first (anything consistently above 85–90°C under load is suspicious), then run a memory test, update or roll back drivers, and inspect the power supply. Work through the steps below in order — most random-restart problems are solved within the first few.
What Random Restarts Actually Look Like
Not every unexpected reboot has the same cause, and the pattern matters. Pay attention to what happens right before the restart, because that is your best clue:
- Restarts during gaming or heavy work: usually overheating or a power supply that cannot keep up with the load.
- Restarts a few minutes after every boot: a failing driver, a bad Windows update, or a component that fails as it warms up.
- Restarts with a blue screen (BSOD) flashing briefly: Windows crashed — the error code on that screen identifies the culprit.
- Restarts without any warning or error: more often hardware: PSU, RAM, or overheating triggering an automatic protection shutdown.
If you see a blue screen, disable automatic restarts first so you can read the error code: open Control Panel → System → Advanced system settings → Startup and Recovery → Settings and uncheck “Automatically restart”. The blue screen of death (BSOD) will then stay on screen long enough for you to note the stop code.
Step 1: Rule Out Overheating
Heat is the number one cause of random restarts. Modern CPUs and GPUs protect themselves by shutting down or restarting when temperatures get dangerous, so a dusty cooler can cause exactly this behaviour.
Check your temperatures
Install a free monitoring tool and watch your CPU and GPU temperatures at idle and under load. Our guide on how to check CPU temperature explains the tools and what the numbers mean. As a rough rule of thumb: idle temperatures should sit around 35–50°C, and anything regularly crossing 85–90°C under load deserves attention.
Fix the cooling
If temperatures are high:
- Open the case and clean dust from fans, heatsinks, and vents with compressed air (PC off and unplugged).
- Make sure all fans actually spin when the PC is on.
- Check that the CPU cooler is firmly mounted — a loose cooler loses contact with the CPU.
- If the PC is more than 3–4 years old and runs hot, the thermal paste between the CPU and cooler may have dried out; replacing it is a cheap fix.
For a full walkthrough, see our guide on how to fix high CPU temperature. High graphics-card temperatures can cause the same symptom during gaming — check our guide to how to check GPU temperature as well.
Step 2: Test the RAM
Faulty or badly seated memory causes crashes and restarts that look completely random. The RAM holds data the CPU is actively using, so even one failing module can corrupt what the system is doing and force a reboot.
- Power off, unplug, and reseat the RAM sticks: remove them, blow out any dust from the slots, and click them firmly back in until the clips lock.
- Run Windows Memory Diagnostic: press Win + R, type
mdsched.exe, press Enter, and choose “Restart now and check for problems”. The PC will reboot into the test. - If you have two or more sticks, test them one at a time to isolate the bad one.
For a deeper dive into memory testing tools and interpreting results, read our guide on how to check RAM health.
Step 3: Check the Power Supply (PSU)
The power supply unit converts wall power into the voltages your components need. When it ages or was never powerful enough for your hardware, voltage drops under load and the system restarts without warning — often with no blue screen at all. This is the classic “restarts while gaming” cause.
- Add up your components’ power draw and confirm your PSU’s wattage rating leaves a comfortable margin (roughly 20–30% headroom is sensible).
- Check that both the 24-pin motherboard cable and the CPU power cable (4-pin or 8-pin near the top of the board) are fully plugged in.
- If you recently added a more powerful graphics card without upgrading the PSU, that mismatch is a prime suspect.
- Listen for odd noises — buzzing or clicking from the PSU is a bad sign.
PSU testing at home is limited; if everything else checks out and the restarts continue under load, swapping in a known-good PSU (borrowed or bought with a return option) is the definitive test. Never open a PSU yourself — its internal capacitors can hold a dangerous charge even when unplugged.
| Cause | Typical signs | First check |
|---|---|---|
| Overheating | Restarts during gaming or heavy tasks | Temperature monitoring |
| Failing PSU | Instant restarts with no error, especially under load | Wattage margin, cable seating |
| Faulty RAM | Restarts at odd times, sometimes with memory error codes | Windows Memory Diagnostic |
| Bad drivers | Restarts started after a driver or Windows update | Device Manager, driver rollback |
| Overclocking instability | Restarts only when overclock is applied | Reset to stock speeds |
Step 4: Update or Roll Back Drivers
A corrupt or incompatible driver — most often the graphics driver — can crash the whole system. If the restarts began right after a driver update or a Windows update, that timing is strong evidence. Our detailed guide on how to fix Windows 11 driver problems covers the full process, but the essentials are:
- Update your graphics driver to the latest stable version from the manufacturer’s site.
- If the problem started after an update, roll the driver back in Device Manager: right-click the device → Properties → Driver → Roll Back Driver.
- Run
sfc /scannowin an elevated Command Prompt to repair corrupted Windows system files.
Step 5: Check for Malware and Software Conflicts
Some malware forces reboots as part of its behaviour, and a scheduled task or background program can do the same. Run a full scan with Windows Security (or your antivirus), then check Task Scheduler for any suspicious reboot tasks. If the restarts happen only in Windows but never in the BIOS/UEFI screen, software is more likely the cause; if they happen even in the BIOS, it is almost certainly hardware.
Step 6: Reset Overclocks and BIOS Settings
If your CPU, GPU, or RAM is overclocked, return everything to stock speeds. An overclock that was stable for months can become unstable as components age or as summer heat arrives. Also try loading the BIOS/UEFI default settings — a corrupted BIOS setting can cause restarts, and defaults eliminate that variable. Do not update the BIOS firmware unless you have a specific reason; a failed BIOS update is riskier than the problem it might fix.
Step 7: Inspect the Motherboard and Cables
With the PC unplugged, look for swollen or leaking capacitors on the motherboard (small cylinders with bulging tops), and confirm every power cable is fully seated — the 24-pin ATX, the CPU power connector, and the PCIe cables to the graphics card. A half-seated cable can deliver unstable power that restarts the machine under load.
When to Get Professional Help
If you have worked through every step and the restarts continue, the fault is likely a dying motherboard, PSU, or CPU — components that are hard to diagnose without spare parts. At that point, a repair shop’s bench testing is cheaper than buying parts to guess. Bring them your notes on the restart pattern (under load, at idle, with or without a blue screen) — that information saves them diagnostic time and saves you money.
If your machine does not restart but instead freezes completely, the diagnosis is slightly different — see our guide on how to fix a PC that freezes under load.
Frequently Asked Questions (FAQs)
Why does my PC restart only when gaming?
Gaming pushes the CPU, GPU, and PSU to their limits simultaneously. The usual culprits are overheating, an under-powered or ageing power supply, or an unstable graphics driver. Check temperatures and your PSU’s wattage rating first.
Can a Windows update cause random restarts?
Yes. A problematic update or an incompatible driver delivered through Windows Update can destabilise a system. Check Settings → Windows Update → Update history and uninstall recent updates to test. Microsoft also occasionally pushes fixes for known bad updates, so keeping the system fully updated matters too.
Is it safe to keep using a PC that randomly restarts?
Not really. Beyond lost work, abrupt restarts can corrupt files and damage the Windows installation over time. If the cause is a failing PSU, it can in rare cases damage other components. Diagnose it sooner rather than later.
How do I find out why my PC restarted?
Open Event Viewer (Win + R, type eventvwr.msc), go to Windows Logs → System, and look for critical “Kernel-Power” events and errors around the restart time. These entries often name the failing driver or component.
Could a faulty hard drive or SSD cause restarts?
It is less common, but a failing drive with bad sectors in critical system areas can cause crashes and reboots. Check drive health with the manufacturer’s tool or a SMART monitoring utility; if the drive is failing, back up your data immediately and replace it.
The Bottom Line
Random restarts feel chaotic, but they almost always come down to heat, power, memory, or drivers. Start with temperatures, then RAM, then the power supply, and work down the list — in most cases you will find the cause within the first three steps. Fix the underlying problem rather than living with the reboots, because every unexpected restart risks your data and stresses your hardware.
Last Updated: 8 October 2026
About the author: Zaviyar Sultan is a UAE-focused writer at Paxi, covering driving, visas, banking, insurance and everyday UAE life. His guides are researched from official UAE government and regulator sources and updated regularly.
Paxi is an independent informational website, not affiliated with the UAE government or any agency mentioned; content is general information only, not legal, immigration or financial advice; verify critical details with official sources before acting.