Please help me here, can't seem to figure this out..

So I have an ASUS PC Computer, and I haven’t used it in months, so it’s not in bad condition and all, and I decide to put a setup backup so I can start web development, long story short I shut down the computer during a system reset when it was trying to reinstall windows ( I know im stupid ), I managed to get it to turn on, and install windows all over again without shutting off, and all of a sudden, when windows is reinstalled, it does the same thing, so the procedure goes like this:

• Turns on (and after like 2 seconds..)
• Turns off (and after like 2 seconds..)
• Turns on (and after like 2 seconds..)
• Turns off (and after like 2 seconds..)
• THIS WILL KEEP REPEATING UNTIL I GET A 10% CHANCE THAT THE BELOW HAPPENS vvvv
• 1/10th chance that it will turn on and stay on, however after 30 minutes, turns off, same procedure happens as above, and this happens after I only press the power switch once, so the computer keeps trying to turn on then turns off.

I gave it a new power cable and it turned on fine 3 times and when I used it for 30 minutes the same thing happened, I would fix it / replace it, however I don’t know if the problem is with my motherboard, or the problem is with my PSU, because I don’t wanna spend too much money on both a PSU and a motherboard because i’m on a budget.

Also I cannot check my hardware but it is an Asus PC, with Intel core i7, and Nvidia Geforce GTX760, that’s probably all I remember.

Please help me do this, any help is appreciated.