What troubleshooting steps can fix startup crashes on Ryzen/NVIDIA PC?

[OliviaXH]

I just finished building a new gaming PC with an AMD Ryzen processor and an NVIDIA graphics card, and I'm experiencing a consistent crash on startup whenever I try to launch any demanding game or benchmark. The system boots into Windows fine, but the moment the game loads, the screen freezes and I'm forced to hard reboot. I've updated to the latest GPU drivers using a clean install, checked my RAM with MemTest86, and monitored temperatures, which all seem normal. For anyone who has solved a similar issue, what should my next troubleshooting steps be? I'm wondering if it's a power supply problem not delivering enough stable power under load, a potential BIOS setting related to the PCIe slot, or some obscure conflict with background software.