My PC Crashes When Playing Certain Demanding Games – Need Help Fixing This!

I've been using my PC for about 18 months, and it has run perfectly until recently. For some reason, it crashes only when playing certain high-demand games like Poppy Playtime 2, Fortnite, and Ark Ascended. I can still play lighter games like Minecraft and Geometry Dash without any issues, so I know the specs should be fine. I have a 3060 ti graphics card, an R9 5900X processor, 32GB of DDR4 RAM, 500GB of M.2 storage, and 1TB of slower storage. I've already tried several things to troubleshoot: I replaced the thermal paste three times since I thought it might be a heat issue, and I checked and reinstalled all my drivers. I even lowered the graphics settings and resolution, but I still experience crashes. Initially, I'd get a blue screen of death, but now the game just freezes, and I have to reboot my PC to get out of it. With Poppy Playtime 5 coming out soon, it's frustrating that I can't play the previous games. I'm determined to fix this myself and would appreciate any suggestions on what else I could try!