Please help me diagnose a hard crash issue!

My computer has been hard crashing recently. It first started around December 2025. I would turn the computer on and for an erratic point, suddenly hard crash. My monitor would show no display, the computer would stay running for a while, then attempt to reboot itself. Sometimes my PC would disable the audio driver. If successful, it'd work for a while and do the process again.

If unsuccessful, it'd attempt to POST then get stuck, with no display but everything running. The power and reset buttons would be unresponsive and I'll need to shut off the power from the PSU directly.

I checked Event Viewer. It tells you nothing about the crash, just that there was an unsuspected shutdown of all processes. Probably a hardware issue. So, I managed to boot the computer into the UEFI and leave it sitting while checking temps. Temps were fine, but the computer also shuts off while in UEFI!

Unsuccessful solutions:

• Removed and tested all components one by one, including external components, except for the motherboard, CPU and PSU. I don't have spares.
• Reset CMOS
• Tried using the APU only.
• Tried updating UEFI/ Windows 10/ Chipsets
• Held power button for 30 seconds after turning off PSU.
• Cleaned PC
• Reapplied thermal paste solution

Successful temporary solution:

I left my PSU turned off for a few hours and this seems to prolong the amount of time the PC works based on how long my PSU was turned off. If I left it off for a few hours, I can likely use my PC normally for a few hours to a day. If I left it off for over 2 days, I can use it for more than a day to even a few months. I had no issues since the start of January 2026 until a week ago.

Clearly, it's a hardware issue at this point. I'm thinking that it may either be the PSU, the CMOS battery, or motherboard. But, there's also the possibility that it could be the CPU, too. I can't afford to spend money flippantly, so I'm wondering if anyone here can easily pinpoint which component might be at fault based on this information?