Question Random restarts

[Maxinity]

Recently I figured out that my PSU is causing my pc to randomly restart meaning I have to change it but before I do I'd like to ask 2 questions.

1. Why does my pc always restart except when I play video games?
2. Could this instead be a problem with the cables coming out the PSU and not the PSU itself?

 

[rgd1101]

because game use more resource/power
could if you using some 3rd party cable or the cable is loose