Few things are more frustrating than working on something important and watching your PC keep restarting without warning. Whether it's a sudden reboot mid-game, an unexpected shutdown during a video call, or an endless restart loop before Windows even loads, random restarts almost always point to a real underlying fault — not a quirk you can ignore.
This guide walks through the most common causes we see at our Edinburgh workshop, what you can check at home, and when it's worth booking a professional diagnosis. The same steps apply whether your computer is in Leith, Portobello, Musselburgh, Dalkeith, or anywhere else across the Lothians.
1. Overheating Is the Number One Cause
Modern processors and graphics cards are designed to shut the system down the moment they hit a critical temperature, and that protective restart is the cause of a huge number of "random" reboots. If your PC restarts during games, video editing, or on warm summer days, overheating should be your first suspect.
Common culprits include dust-clogged fans and heatsinks, dried-out thermal paste on the CPU, blocked air vents (especially on laptops), and failing case fans. We've covered the warning signs in detail in our PC overheating guide, but the quickest home check is to install a free tool such as HWMonitor and watch your CPU and GPU temperatures while the system is under load. Anything above 90 °C is a red flag.
2. A Failing or Underpowered Power Supply
The power supply unit (PSU) is the most under-appreciated component in any PC. When it starts to fail or can't deliver enough wattage — often after a GPU upgrade — the most typical symptom is sudden restarts under load with no error message and nothing useful in the Event Viewer logs.
Telltale signs include a faint burning or ozone smell, a buzzing PSU fan, or restarts that get worse the longer the machine has been on. If you suspect the PSU, take a look at our breakdown of power supply failure signs for the full list of symptoms. PSU faults aren't something to muddle through — a dying unit can take other components with it when it finally goes.
3. Faulty RAM
Bad memory is another classic cause of random restarts and blue screens. RAM faults often produce inconsistent symptoms — restarts that happen at different times, blue screens with codes such as MEMORY_MANAGEMENT or IRQL_NOT_LESS_OR_EQUAL, or programs crashing for no obvious reason.
Windows has a built-in memory tester. Press the Windows key, type Windows Memory Diagnostic, and let it run on the next reboot. For a much more thorough scan, the free tool MemTest86 can run overnight from a USB stick. If either flags errors, the affected stick needs replacing — we've also written about how to interpret BSODs if you're seeing those alongside the restarts.
4. Driver Conflicts and Windows Updates
Software-side restarts are often triggered by graphics driver crashes, recent Windows updates, or a conflict with newly installed software. If the restarts started after a specific update or a new program, that's a strong clue.
Things to try:
- Roll back the most recent graphics driver via Device Manager.
- Use the GPU vendor's clean uninstall tool (DDU) and reinstall the latest stable driver — not always the newest beta.
- Check Windows Update history for failed installs and see our guide to fixing Windows Update errors.
- Boot into Safe Mode for an hour. If the restarts disappear, the issue is software, not hardware.
5. Malware and Rogue Background Processes
Some malware triggers restarts deliberately to disable security tools or to load earlier in the boot process. If your PC restarts at suspiciously specific times — for example, every time Windows Defender starts a scan — it's worth ruling out an infection. Our virus warning signs guide covers what to look for.
6. The "Automatically Restart on System Failure" Setting
By default, Windows restarts the moment it hits a critical error, which means many users never see the blue screen with the error code that would actually identify the fault. Turning this off doesn't fix anything, but it lets you read the message:
- Press Windows + Pause/Break and click Advanced system settings.
- Under Startup and Recovery, click Settings.
- Untick Automatically restart, click OK, and reboot.
Next time the PC crashes, you'll see the stop code on screen — write it down, it's gold for diagnosis.
7. Failing Storage Drive or Loose Cables
A dying SSD or hard drive can cause Windows to restart when it tries to read corrupt sectors. Open Command Prompt as administrator and run chkdsk /f /r, then check the drive's SMART status with a free tool like CrystalDiskInfo. While the case is open, it's also worth reseating the SATA, power, and RAM cables — vibration over years can loosen connectors. We've covered the wider failure pattern in our hard drive failure signs post.
When to Stop Troubleshooting and Get Help
Random restarts that happen before Windows even loads, restarts paired with strange smells or noises, or any restart loop after a power surge are all cases where DIY fixes can do more harm than good. The same goes if you've already opened the case and aren't fully confident reseating components without static protection.
Our hardware diagnosis and upgrade service covers everything from PSU and RAM testing to thermal repastes and fan replacements. If the cause is software-side, our software troubleshooting service can usually resolve it without a full reinstall — and if the worst happens, our data recovery team can rescue files from a failing drive before it's too late.
If you're in Edinburgh or anywhere in the surrounding areas, you can book a repair online or use our home callout service if you'd rather we came to you.