This only happens with Overwatch.

It will restart, no blue screen, no error message, and boot up again like normal. PC is not overheating.
It doesn’t happen with any other game. I can run RDR2, BG3 and other intensive games forever without any functionality issues. Only Overwatch is causing my PC to shut off.

I uninstalled game, verified game files, lowered my graphics settings. No solution.

I was worried it was a PSU issue but if so, why are no other games causing this to happen?

I have an i5 CPU, a GTX 1070 GPU and a CX600 PSU.