Why Does My PC Randomly Shut Down Without Warning?

I've been experiencing some really frustrating random shutdowns with my PC over the past couple of weeks. It seems to happen at random times – while gaming, watching YouTube, or even just studying. There's no specific pattern. The shutdowns are sudden and leave no trace like a BSOD or freeze; it just powers off. When I check Windows event viewer, it shows a Kernel Power 41 (63) error, but no other related events.

Here's my build to give some context:
- CPU: 9800X3D
- GPU: MSI GAMING TRIO 5070 TI
- Motherboard: MSI MPG X870E CARBON WIFI 7
- RAM: CORSAIR 32Gb 6000MHz
- PSU: MSI A1000G 80+ GOLD
- AIO: MSI MAG CORELIQUID I360
- Fans: 6 MSI EZLIGHT

So far, I've tried:
- Reinstalling GPU and chipset drivers using DDU
- Updating the BIOS to the latest version
- Running stress tests with Superposition and OCCT, which showed no errors or shutdowns; temperatures were normal (CPU at 86°C, GPU at 60°C)
- Running sfc and DISM
- Updating to the latest Windows version
- Memtest86 passed with no issues

What's next on my list:
- Trying a different power cord
- Reinstalling Windows

I don't think it's a hardware issue since all tests came back clean. However, I've noticed some weird voltage readings (12V displaying 24V, and so on), which might just be errors. One thing that I remember is changing a setting in the Nvidia app for 'prefer max performance', which I reverted to default shortly after. Interestingly, the shutdowns seem to coincide with moments when I notice a network error, usually while gaming.

For clarity, I haven't done any overclocking; I've had the PC for about a year and the GPU since Christmas 2025. I'm really at my wits' end with this issue, so any insights or suggestions would be greatly appreciated! If you need more info, just ask and I'll respond quickly. I even swapped the PSU for a new one, but the problem persists.