9070xt - PC crashing in games, stuttering too

I recently upgraded my PC with a 9070 XT, but the rest of my system is a bit older:

• RAM: 32 GB (3200 MHz)
• CPU: Ryzen 7 3700X
• Motherboard: Gigabyte B570X Aorus Elite
• PSU: 850 W

At first, everything was great-250+ FPS in games, smooth performance but suddenly I started getting stutters, crashes then BIOS resets. The PC itself is 5 years old and it ran fine before the GPU upgrade, so I’m a bit lost.

I updated the BIOS from the 5-year-old version to the latest one in one big jump (probably not ideal), and now the system seems stable except games still stutter and eventually crash.

The latest issue: when I try to enter BIOS, it loads, says settings have been reset, I hit OK, and then I get a black screen.

From what I’ve read, it might be the CMOS battery failing to hold my new BIOS settings and XMP profiles.

But can boot normally and use the pc just not game...

Has anyone experienced this? Could the CMOS battery really be the culprit, or is something else going on? Any advice would be massively appreciated!