I would be interested if there are any clues in the Windows Event Log...
The easiest way to check the Event logs is to do the following...
In Control Panel, navigate to Administrative Tools and click on Event Viewer.
Expand the Custom Views folder and click on Administrative Events.
The Administrative Events contain Warnings, Errors, and Critical events from all event logs.
Windows 10 -
In Control Panel, enter event in the top-right search box and click View event logs in the result.
The Event Viewer can be really confusing, there are a lot of warnings, errors, and informational messages. Without knowing what it all means, you can incorrectly assume that your computer is broken or infected when there’s nothing really wrong.
The events themselves are what you want to see, but the usefulness of these events can range from being very specific and obvious things that you can fix easily to the very vague messages that don’t make any sense and you can’t find any information on Google.
Unless you are experienced enough with determining which event errors are significant you may not find anything which is going to point you in a direction which will help with diagnosing issues with a computer.
Because of the ambiguities that are iherent in these event errors there are scammers out there who will access your computer with your permission and will quote event errors from the event viewer to convince you that your computer is infected and charge you to "repair" the computer.