I left out one, possibly, important thing.
The last thing that I did last night before shutting down was to adjust the paging file setting.
As shown on this webpage:
https://www.tecklyfe.com/possible-fix-windows-10-running-very-slow/
I set the paging file to the recommended size on my laptop.
There is no way of knowing if that was a cure without going back to the orginal settings.
But first, an entire system backup is in order.
