[SOLVED] PC randomly turns off, then back on itself immediately. Help!

[parama3500]

It's not when I'm doing something intensive, also happens when it's idle; so possibly not a heating issue. (didn't check the temps tho but sure they are under control)

I'm just doing something on my PC and screen goes black, fans turn off, just as if the electricity went down, then 1 second later it starts to boot again.

Again, I can work for 10-20 minutes and same happens.

Specs:
i3 4350T + stock fan
4GB 1600MHz RAM
Asus ROG Strix GTX 1660 Ti
Samsung 860 EVO 500GB (System)
1TB HDD + 320GB HDD
Corsair CX650M

(no oc on any part)

CPU, RAM, Mobo are 2 years old, rest just 6 months old.

This issue started last month with the PC freezing and staying frozen until I turn it off manually. It also froze in the BIOS once.
It kinda fixed it itself and now I have this restart loop problem.

 

[Ralston18]

Power off, unplug, and open the case to check that all cables, cards, RAM, jumpers are fully and firmly in place.

Clean out dust and debris as well.

Likewise check the power connections from wall outlet to computer and everything (if anything) in between.

Could be a bad/loose power cable or a problem in the wall outlet.

Next suspect - PSU. Even if new.....