Your computer was restarted because of a problem? kernel? What's the problem???

That indicates it had a Kernel Panic. If this was the only one, it's likely nothing to be concerned about. However if they continue to occur please post the latest KP report which you can find by doing the following:

1. Launch Console.
2. In the Console app sidebar, select the folder named Library/Logs.
3. Select the DiagnosticsReporter folder.
4. A list of reports is displayed. Select the most recent crash report to 

Work thru the steps, at > If your Mac restarted because of a problem - Apple Support

Another great tool to help find problems, is > https://apps.apple.com/us/app/etrecheck/id1423715984?mt=12