This has happened to me twice now, with 2 separate Win10 upgrades.
On both occasions it started when, on shutdown I was asked to "install updates and shut down" instead of the normal "Shutdown". Over several days, this happened every time I shut down, until I eventually decided something was wrong and went to Windows Update. There it tells you the PC needs to be restarted to install updates. If you click on the Restart option there, the updates are installed.
What does that restart do that isn't done with Shut down and reboot?
BTW, as of the latest update, Cortana no longer finds "Windows update". Instead it offers "Check for updates" which takes you to Settings > Windows Update! WTF?
And, am I the only one who finds the M$'s unsuccessful attempts to get rid of Control Panel (starting with Win8) a waste of time and a great annoyance? It's got to the point where Cortana is the only way to find out where each setting is hidden. I have resorted to put a shortcut to Control Panel on my desktop. That way I have a simple way to access to most settings.