Random BSODs and random restarts while gaming – need help diagnosing my PC

Can someone help me figure out what’s wrong with my PC? I’m getting random BSODs and random restarts, and I can’t figure out what’s causing them.

My PC specs:

• SSD: MSI M480 PRO 2TB
• Motherboard: ASUS X670E-A
• GPU: RTX 4090
• PSU: DeepCool PX1200G 1200W
• CPU: Ryzen 7 7800X3D

I tested the system with OCCT, including stress tests, and everything seems fine. There are no obvious errors or crashes during the tests.

However, when I start playing Cyberpunk 2077, everything can look completely fine for about an hour, and then the PC suddenly restarts and boots back into Windows.

I’ve also experienced random BSODs and some strange Windows crashes. At one point, one of my SSDs was disappearing from Windows, so I suspected the SSD might be the problem.

I removed that SSD from the system and tested again, but I still experienced a random restart.

I also checked the GPU power cable and made sure it was properly connected.

What would be the most likely cause of this?

Could this be the motherboard, CPU, PSU, GPU, RAM, or something else?

OCCT doesn’t seem to reproduce the problem, so I’m not sure how to properly diagnose it.

Any advice on what I should test next would be greatly appreciated.