Full PC crash when playing Fortnite.

Pls help I been trying to fix my potato of a pc for 3 months at this point. Basically whenever I try play Fortnite 90% of the time my shit hard crashes im talking game starts freezing audio makes robot sounds in my damn ears then I black screen my keyboard and mouse lights turn off but my pc lights and fans are still on. I gotta force shut it down flip the back switch wait a few second flip it again and turn her back on. Now the times she doesn’t do this, it works perfect I can play for HOURS at a time then the next day I get 5-30 min in and crash every single time. I know my system can handle the game I’ve stress tested all my hardware gotten an brand new psu, swapped my 3060 rtx w a 4070 to try it out and it still crashed. I’ve also wiped my whole pc and started fresh, rolled back nvidia drivers, repaired files, updated bios, changed pcie from auto to gen 3, turned off exmp, turned off fast start up, turned off HAGS. please help cuz I’m about to throw this shit out the window

Full specs:
Msi B550M pro-vdh wifi
Ryzen 5 3600
GeForce Eagle rtx 3060
Corsair 850w gold
Cooler master liquid cool ml240l rgb v2