It is difficult to diagnose a sudden PC restart problem because when it restarts there is no error message that gives us a clue. To solve this problem, we must first know what are the causes that can cause a PC to restart itself.
In most cases, the sudden restart of a PC is due to disabled RAM modules. Generic memory modules have in particular small defects that can make the PC not to work properly. It is necessary to examine the memory with Memtest86: RAM tester The Memtest results are easy to analyze: If the home screen retains the same table after at least one complete pass, we can estimate that the memory is in good condition. If additional lines appear, the memory is defective.
For example we can choose the Corsair ram that is reliable (lifetime warranty) and good quality.
Tip: If your motherboard supports it, then you can purchase two modules to take advantage of Dual Channel mode. To use this mode, it is imperative to use two identical modules (of the same brand) and that are of good quality, not generic.
If that does not work, it may be necessary to restart the PC with a minimal amount of peripherals. Disconnect CD drives, recorders, Internet connection, (modem), printer, complementary hard drive disk, etc. Try again until the PC no longer restarts alone. When the rebooting stops, reconnect the peripherals one at a time until the problem happens again.
Look at the temperature of the processor, if it is too high, install a more powerful fan. To know the temperature of the processor, just use the utility that comes with some motherboards, or the Everest program.
Tip: If necessary, it would be good to remove the dust that is in the casing with an air pump for example. This will not only reduce considerably the noise of the PC but in some cases it will be able to decrease the ambient temperature of the PC and therefore, of the processor.
Defective Power Supply
In this case the solution is to switch power for a more powerful supply, hoping this will solve the problem or have it examined by a professional.
The restart may also be due to an interference from your utility company's electricity grid. You can ask the utility company to come and check the power grid. If this is indeed due to interference in the electricity network, the company must do what is necessary, but in the opposite case, the displacement of the personnel may be in your charge.
Check that the memory frequency is correct and that the latency time is according to the factory settings.
You can also do a BIOS update, by going to the motherboard manufacturer's website. Do not forget to back up your current BIOS to an external media. Be careful because a power failure during BIOS update would be fatal for this one!
Among the problems that are due to the computer itself and its components, viruses are added. They are even considered as one of the main causes of restarting the PC. In this case, there are several viruses and their derivatives that are capable of causing such inconveniences among which the celebrated Sasser and Blaster.
Tricks for Windows
How To Disable Automatic Restart
So that the PC does not restart itself, sometimes only one action is needed, but it is not always effective:
1) Go to the Start menu, then Control Panel then Performance and Maintenance and finally System (or right click on My Computer and select Properties).
2) Click on the Advanced tab
3) On Start and Recovery Click on Settings
4) Uncheck Automatic restart
1) Click the Start button
2) Click on Run ...
3) Type shutdown -a
4) Click OK
This operation is only valid for Windows XP!
Open Windows Event Viewer
You can read the error message(s) generated by the system using the Event Viewer. To access this:
1) Go to the Control Pane, then Administrative Tools
2) Double-click Computer Management
3) Open the event viewer (section System Tools) and read the error messages.
Now you just have to do a Google search with the words and error codes of the error message that are most relevant and find people who have had the same problem, and possibly the solution to your problem!