Question Upgraded PC and now it reboots when launching games ?

Aug 9, 2022
Hey, i was wondering if anyone could help me out. I just upgraded my PC. I went from a 850 watt PSU to a 1200 watt PSU in preparation of the 4000 gpu cards coming out. I also swapped out my 3900x for a 5800x3d. All my temps are better than before. And even when i launch a game, the cpu stays at 40-45 and the gpu is between 50-60. But it immediately reboots a couple seconds in. Temps never spiked or anything. I read it could be the power supply not supplying enough power, but at 1200 watts i cant see that being the problem. The PSU is EVGA 1200 watt P3 Platinum. Could I have received a faulty PSU?

Also, i should mention, i switched cases to a Hyte Y60 which uses a riser cable. Could that be it? I tried a furmark stress test and i had no issues there. And it is only rebooting when i launch a game, never when I'm doing other tasks. I honestly don't know where or what i could have done wrong.