I built a computer for a friend recently. At times, for no apparent reason, it becomes way too slow to game (dropping from ~100 frames in Fortnite for example to 10). Since yesterday, it is very slow at boot up, or won't boot at all, getting stuck at this: https://streamable.com/ovna2u
3600X
B450 Tomahawk Max
P1 1TB
Corsair TX650 iirc
GTX 780 Ti (used, looks to be working fine though)
16GB 3200MHz RAM
Latest nvidia drivers, latest windows updates etc. Any ideas what the culprit could be?