I have a corsair rm850, rog strix b360-F gaming motherboard and a 2070 superI would try updating BIOS on motherboard, it might help
What are specs of PC?
what PSU do you have?
It happends right after the screen goes black. The fans spin up quickly then stop after a couple of seconds around the same time the leds inside my pc turn offis this while windows is still showing the shutdown screens or after screen turned off?
if you have an ssd, try turning this off and see if it makes any difference - https://www.tenforums.com/tutorials/4189-turn-off-fast-startup-windows-10-a.html