Thanks for uploading the System log, it is a useful source of error and warning messages and does often help in diagnosing problems.
In your log I can see the many error 41 messages indicating that Windows wasn't shutdown properly, these will be the result of the restarts of which you complain. Whilst I do see several other error or warning messages that are of concern I don't see any error messages that can convincingly be said to be the cause of these restarts.
How does it restart? Does it power off and you have to restart it manually? Does it do an auto-restart on it's own? Does it do something else?
Have you checked temperatures yet? If not please
download HWMonitor (free) and run that. Expand the CPU temperatures section so we can see every CPU core. Then post a screenshot of those temperatures when the PC has been completely idle for five minutes. Then post a second screenshot of those temperatures when you are working the CPU as hard as you possibly can.
It will be handy to see more troubleshooting data, so can you please download the
SysnativeBSODCollectionApp and save it to the Desktop. Then run it and upload the resulting zip file to a cloud service with a link to it here. The SysnativeBSODCollectionApp collects all the troubleshooting data we're likely to need. It DOES NOT collect any personally identifying data. It's used by several highly respected Windows help forums (including this one). I'm a senior BSOD analyst on the Sysnative forum where this tool came from, so I know it to be safe.
You can of course look at what's in the zip file before you upload it, most of the files are txt files. Please don't change or delete anything though. If you want a description of what each file contains you'll find that
here.
In addition, look in the folder C:\Windows\LiveKernelReports. You may see several sub-folders, look in each sub-folder for dump files (.dmp) and upload all those that have a timestamp within the last month.