Gaming PC won't boot up but randomly turns on for a few seconds when left alone

[calisntwright]

I tried to turn on my custom gaming PC yesterday but nothing happened. Everything was working perfectly only hours before this and i have no idea what could be causing the issue. Interestingly, the mouse and keyboard are lit up despite the PC not actually booting up- so i suppose this must mean that the PC is receiving power. Another thing that i can't really explain is the fact that when i leave my PC plugged in it randomly turns on for a few seconds at unpredictable times. After this, it dies and nothing else happens.

I honestly have no idea why this might be happening and any solutions would be appreciated.

Thanks a lot

 

[alexoiu]

try testing the power supply: https://www.youtube.com/watch?v=5FWXgQSokF4
See if a fan connected to it does spin.