Had a weird thing happen. "Configuring security settings"

Running Windows 10 Pro, latest version.

I wasn't really doing anything unusual, just watching a boring Youtube video. The computer freezes up--like in the old days. Totally frozen. I haven't had a total freeze up since XP, like over 3 years ago. Neither the kb nor the mouse were responsive. I was getting a lot of disk thrashing, though.

So, I tried Esc, Ctrl-Alt-Del, various Ctrl combinations, nothing was working. Then after maybe about a minute the blue screen with various options, including task manager, finally came up. Then I found I was eventually able to close the browser and a few other programs that were open.

During all these "goin's on" a couple times I happened to catch a glimpse of a screen that looked like a Windows Update type screen. There was an image of a gear and a message that said, "Configuring security settings." I don't recall EVER seeing that before.

I went into the Windows Update history, but there was no indication that any new updates had been installed.

Has anyone ever seen that before? I wasn't doing anything that would have triggered a configuration of security settings, if there even is such a thing. Once I got everything closed I did a restart and haven't noticed any problems. It has me concerned, though, because there were no Windows updates installed and I can't imagine what would have caused that weird behavior.