CPU keeps overheating after longer periods of load

Hey there,

so I'm having a big problem with my PC.

At first, the specs:

CPU: AMD Ryzen 9 5900X (24) @ 3.700GHz

GPU: AMD Radeon RX 6800 (sienna\_cichlid, LLVM 14.0.6, DRM 3.47, 5.19.13-arch1-1)

Motherboard: MPG X570 GAMING EDGE WIFI (MS-7C37)

RAM: 32GB@3600 MT/s

PSU: 850 Watt be quiet! Straight Power 11 Modular 80+ Gold

The problem:

The CPU is - seemingly at random - overheating to 105 - 110°C, throttling at first, then shutting down in the process. It's worth noting that I had this PC for 2 years now. This problem is new and occurred first around 3 - 4 weeks ago, but only once. It hasn't occurred for a week and I kinda forgot about it, until I recently popped up again. Now, I'm having the problem almost daily when playing games or compiling stuff.

Why do I know it's overheating? My BIOS warned me once when I tried to turn it on again, then I kept running \`watch -n 1 sensors\` to keep an eye on the temperatures. There, I can see that the temps are indeed rising above 100°C.

At first, I thought it's a hardware problem, so I removed the cooler (an AIO from be quiet), removed the thermal paste, reapplied fresh stuff and reseated the cooler. However, nothing changed - I still had a crash around an hour later. The fans are also not the problem ,they are definitely spinning at full speed once the temps reach 70°C.

Now the interesting part. After I pulled a few stress tests (I used \`stress --cpu 32\` and \`stress --cpu 128\`), I noticed that the temps would stay around 68°C for a while. However, after \~10 minutes, the temps would rise WAY higher, reaching 80°C - 90°C. Now, when I abort the stress test and all the processes disappeared (confirmed this with btop), the temps dropped slightly to \~70°C, but keep rising again, even tho there is nothing running that could cause such a strain on the CPU. I literally just booted the PC and there is nothing started automatically except system services.

Another interesting thing is that, even when I shut the PC down before it hits 100°C, and then turn it on and enter the BIOS, the CPU will keep overheating and turn off at some point.

My only idea is that the CPU is dead or malfunctioning but I have no clue why that would be the case. I've never had a CPU dying on me, even after over 10 years of use, and this one is barely 2 years old. If someone has an idea how to debug this problem, I'd greatly appreciate any help I can get - I'm completely at a loss here