i9 9900k on Aorus z390 Ultra - pc randomly restarts itself when system is not on stress.

[HUmbr]

 On my Z390 AORUS Ultra with I9 - 9900k
PC just restart itself on critical error (in event log) without any bluescreen or else, and just restarts, but the strange thing is that it don't happen when PC is on stress load, benchmarking or gaming, but it always happens on low load - as working process in Photoshop or just serfing web in browser, or just system was idle for some hours.
I tried update the drivers, I updated my Bios (updates of Bios didn't helped, last update just make it reset bios settings after crash), I tested RAM, I dont know what is the problem causing it.
Attaching event_config files, if the size is too big, then providing google drive url:
https://drive.google.com/file/d/1lb0QNFzmyb7zUc4oNe-IGCTuo1Fo9cxf/view?usp=sharing

[HUmbr]

Also I read another post that is connected with RAM, but its not my case, RAM is showing ok in all tests and XTU, System wont crash during tests, but only one:

It is - Critical Error, Event ID 43 - Kernel - Power
The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.

And this dont explain anything, that's why I pinned logs here, as I said before it just dont happens when system is on stress test except only 1 - XTU (Intel extreme tuning utility) The crash happens if testing the system with benchmark type 1, but wont crash on benchmark type 2

[n_scott_pearson]

Event Id 43 just means that it detected, when Windows was loading, that the system was not shutdown properly. That is, it simply means that the system spontaneously reset (or lost power). Unfortunately, it doesn't tell you diddly squat about why this occurred.

Spontaneous resets are typically the result of a hard system lockup. The Watchdog Timer resets the system to wake the system back up. The most common hard system lockup is a memory bus lockup, which typically occurs if the noise on the memory bus is so high that data bits cannot be distinguished. This could be either a fault in the memory , a fault in the DIMMs, a fault in the memory bus (problem on the motherboard) or a fault in the processor's memory controllers. Secondary causes for system resets include faults in a driver, though most of these result in a BSOD. If a BSOD is occurring, you will find a dump file in the Windows folder.

Hope this helps,

...S

[AlHill]

Have you contacted gigabyte for support?

Do you have adequate cooling?