Aug 29, 2020

Very short intro:
I move back and fourth twice a year, and bring my pc with me I have done this for 3 years with this system. At the same time I apply new thermal paste and do a deep clean.
After the latest one of these a strange new behavior has appeared.

MOB: msi x570 mpg gaming plus
GPU: RX 5700 XT
CPU: Ryzen 7 3700X
RAM: G.SKILL 16 GB Trident Z DDR4
PSU: Seasonic FOCUS Plus 750W


The MOB has EZ-debug-LEDs, when booting normaly each of them turns on for a second or so and then off followed by boot.
Now the CPU led stays on for a few seconds, then the other ones rapidly turn on and off once, followed by fans and RGB turning on. After this nothing happens for a few seconds.
Then the loop repeats, on difference is that the RGB and fans do not turn off.

Now the really strange part, if I leave the system looping like this for ~10-15 min it eventually boots without any problems. I have turn some stresstests and it does not throttle or behave unexpectedly.

So I let it run for a few hours, and played some games. Then turned it off, and on: No problems, normal boot. I rebooted 5 times or so, and everything was as expected.
After this I went to bed, let the pc sit untouched by human hand for 10 hours.

I get up in the morning and power it on, same behavior as before, "boot loop" for almost exactly 10 min, then it started. I waited 5 min, then rebooted, and it was looping again.
Turned the PC over on its side, while power was on, (SSDs), and saw a red led blink that I had never seen before (this was the BIOS flash LED), and then it booted.

Had the problem first when I assembeld the PC, then it was gone for a few days, reappeard again yesterday, first in the morning then in the afternoon, and again now in the morning.

Here we are now. I'm not sure where to start, when it turns on everything runs fine.