For now apparent reason, my laptop was heating up, and the CPU was racing.
I had two browsers open, but they were not doing anything strenuous. So I googled around and found this:
http://news.softpedia.com/news/windows-10-high-cpu-usage-fix-490908.shtml
I applied "Method 1" and it worked instantly. Like a wild horse that suddenly became tame and friendly.
If you use "Cortana" to set reminders for yourself, you should NOT apply this fix, because that's what gets affected. I don't use Cortana for anything, so I'm a happy camper.
How to fix the high CPU usage
Method 1Launch the Registry Editor by typing regedit.exe in the Start menu and navigate to the following path:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TimeBroker
Look for the Start entry and change its value from dword:00000003 to dword:00000004 (simply replace the 3 at the end of the value with 4).
Changing this value could have an impact on Cortana’s performance, but it appears to be closely connected to the high CPU usage in Windows 10. In case you’re not using Cortana at all, you’re on the good side. Otherwise, setting reminders won’t work.