New PC Crashes After a Few Hours of Use—What’s Going Wrong?

I recently built a new PC and it's been running fine initially, but I encounter crashes after a few hours, particularly during gaming. On Saturday morning, after about 3 hours of gameplay, the system crashed to a gray screen with blue lines. After that, every time I tried to launch Wallpaper Engine, it would spike my CPU usage to 100%. Additionally, when I tried to start a game, it reported only having 2 GB of VRAM available, even though my graphics card has 16 GB.

In response to these issues, I decided to reset Windows, thinking it might resolve any driver problems I was facing. I also reinstalled all drivers, flashed the BIOS, reseated components, and adjusted RAM speeds. However, even after those steps, the crashes continued. During my last gaming session, the game froze and crashed again. Now, when I try to launch games, I can't even get past the title screen—everything runs at 1 FPS, and the GPU usage is extremely high despite being idle. I'm also having issues getting any monitors to work other than the primary one.

Here are my specs:
- **CPU**: AMD Ryzen 7 9800X3D
- **Motherboard**: Asus Rog Strix x870-A
- **RAM**: Silicon Power XPOWER Zenith Gaming 64 GB DDR5-6000
- **GPU**: XFX Quicksilver Radeon RX 9070 XT
- **AIO**: Tryx Panorama SE ARGB
- **Storage**: 4 TB Western Digital WD_Black NVME & Samsung Pro 990 2 TB NVME
- **Case**: Hyte Y70 Touch
- **PSU**: MSI MAG A850GL
- **Fans**: 7 LIAN LI UNI FAN SL-infinity 120 MM & 6 Reverse Blade LIAN LI UNI FAN SL-infinity 120 mm Wireless
- **Strimmer**: Lian Li Motherboard 24 Pin & Lian Li GPU 2 x 8 pin Strimmer

Any suggestions on what could be causing these problems?