Get a can of compressed air and a small brush.
Give the innards a good cleaning.
Pay attention to the heat sinks and fans.
Don't forget the psu....a few shots of air from both directions.
Replace the bios battery.
Leave the side cover off and test.
Hi, I built my PC a while ago using Seasonic's 660W +80 Platinum PSU (https://seasonic.com/product/platinum-660/)
I had no issues with it until a few weeks ago when I realized that my PC wouldn't turn on unless I flipped the PSU switch on and off.
However I realized that if I turned the switch off after turning the computer off, I wouldn't have any issues booting it the next day/a few hours later...
But things got a little tricky once my PC started to shut off while playing games. At first I thought it was some heat related issue so I checked my GPU (GTX 980) and CPU (I7 4790K) temps, no problems (They are both at 50/60 during heavy load). I then ran a benchmark (Superposition) to check the PSU's voltage and nothing was out of place (No values were too high/low).
So next I ran a game, thinking my issue was fixed, and as soon as I began playing, my PC shuts off again... After that I have to switch off/on the PSU switch multiple time and press the power button to turn my PC on.
I know this is without a doubt due to a faulty PSU, but seing how the voltage is fine doesn't seem to indicate any problems.
It doesn't seem to be caused by the PSU's temperature because when it shuts down it wasn't hot at all. The fan are also running during load.
I heard that it could also be caused by the motherboard, which mine is a Gigabyte Z-79P-D3.
So what's the issue, is it the PSUc the motherboard or prehaps something else?
Thank you.

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