The Reliability Monitor also only indicates that the computer was not properly shut down.
It looks like the computer is only shutting down. It doesn't look like it's being caused by some software or system error. It seems to be hardware.
This behavior can often be caused by overheating issues. See the temperature your CPU and GPU are reaching.
Several tools allow you to monitor the temperatures of your CPU and GPU. I recommend the free version of HWMonitor.
https://www.cpuid.com/softwares/hwmonitor.html
With temperatures above 80°C, you can start to have problems.
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