Windows Server 2019 Standard reboots by itself

I have an issue with Windows Server 2019 Standard. It's started a few months ago. Machine reboots by itself and there is no helpful information in the Event Viewer at least I couldn't find any.

What I have tried so far.

1. I disabled windows updates
2. I enabled windows clean bootup (disabled all non-essential services)
3. Under Startup and Recovery, unchecked Automatically restart on the System Failure
4. Try to collect dump files using different options like Complete Memory Dump, Small Memory Dump, Kernel memory dump - it doesn't create any
5. Checked system and hard-drive for errors - no errors found

In the Event Viewer. one of the examples:

Event ID: 41 - The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly. Event ID: 6008 - The previous system shutdown at 11:28:47 AM on ‎9/‎2/‎2021 was unexpected. Event ID: 41 - The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly. Event ID: 6008 - The previous system shutdown at 10:08:15 AM on ‎9/‎2/‎2021 was unexpected.

Does anybody have an idea how to collect any information that might lead to the source of the issue?

TL;DR: I would recommend check your hardware if your power supply is functioning properly or if CPU is not overheating to cause the computer shutdown since you didn't found any disks with errors, neither creates them.

Explanation:

You have two Events: 6008 & 41

Regarding 6008: Event ID 6008 entries indicate that there was an unexpected shutdown, as it says. If you press on one of the events with ID of 6008 it might say: "Critical thermal event" - Critical thermal event indicates that the problem is related to one of your hardware components not functioning properly that is triggering the computer to shut down.

Regarding 41 might not contain sufficient information to explicitly define what occurred but probably caused by 6008. Checking your Event both BugcheckCode and PowerButtonTimestamp are 0, this means that something prevents Windows from generating error codes or from writing error codes to disk. Something might block write access to the disk (as in the case of an unresponsive computer) or the computer might shut down too quickly to write the error codes or even detect an error.

More Information: https://docs.microsoft.com/en-us/windows/client-management/troubleshoot-event-id-41-restart