|Normally only overheating of the CPU will cause the computer to shut off and stay off rather than Restart.|
If that's what it's doing
- when the mboard shuts off, the computer will not start up at all, or it will start up but it shuts off again within a few seconds, until the CPU has cooled to below some temp.
- if the computer has had a chance to cool to room temp, the computer will start up fine and run okay until the CPU gets hotter than some critical temp, then you'll get the same symptoms again.
- when the computer does work, the CPU temp will eventually be shown as a lot higher than it being in the range it should be within in the bios Setup current hardware monitor readings.
If it is overheating....
if this is a desktop computer.....
Have you been messing with installing the cpu heat sink yourself ?
If so, you may not have installed it properly.
Are you using overclocking settings or higher than default ram voltage settings in the bios Setup? If so, you may have gone too far - back off on those settings or load bios defaults.
Unplug the case/power supply, or switch off the AC power to it otherwise.
Power off your monitor.
Open up the case by removing the left side panel as seen when you're looking at the front of the case.
If the cpu fan/heat sink has mung (dust, lint, etc.) on it, clean it off, but DO NOT use a vaccuum cleaner to do that (they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components) - use canned air, or an air nozzle if you have access to an air compressor, or an artist's brush that can be used in small spaces, etc. It may be difficult to clean the top of the heat sink under the cpu fan - the most likely place to have mung on it - and the bottom side of the cpu fan blades unless you remove the fan. If you have a case fan, clean that too if it needs it.
Also check for mung on the video card fan and heat sink if it has that, and the power supply's openings / fan.
With the cover still off, restore the AC power, start the computer and make sure the cpu fan spins - if it doesn't spin, if you're sure the power supply is working okay, don't use the computer until you have replaced it.
If it spins too slowly, and/or if it makes rattling or screeching noises, most likely to be noticed when the computer has cooled to room temp, has not been used for a while, and then is started up, the cpu fan's bearings are failing - the cpu is likely to overheat as a result of that if it can no longer spin it's full speed - replace it as soon as you can.