OK, I've toggled the settings. I have no idea what the first option, "automatically based up on mouse or trackpad" means. I checked that, and the scrollbars never appeared. The other, "when scrolling" did, and when I switched back to "always", they came back on here, so I'll see how well it keeps to it, on other pages.
Another wack thing occurring, has been when I move my mouse down the bottom of a window, it sometimes suddenly becomes an entirely different site! And not one that I have open, or even recently had open! This always shocks me (& ****** me off, as I lose whatever I was in the middle of doing), as I've never, in 30 years, seen anything like this happen! And it keeps on doing it, as it did again today, it's like it hits the bottom and triggers a whole different page to open, almost like a butt call on a cellphone... Any idea what is causing this, & how to fix it?