It's happened to me before.
I have two computers, one with an Ad Blocker, one without (I need to open smaller windows for certain websites that Ad Blocker blocks for some stupid reason). When I look at this website without Ad Blocker,
on occasion something knocks me down to the bottom of the page and prevents me from scrolling up.
It's never happened with Ad Blocker, and refreshing the page generally fixes this, so it's a possibility that it's an ad from our Google overlords.
Never really bothered me at all, just refresh the page and it generally fixes it.