reader DC (64-bit) startup tries to show ten images?

I had a previous version (unknown) of reader that worked fine. I just installed Acrobat Reader DC (64-bit) 2021.007.20099. and now whenever I start it (directly or by choosing a .pdf) it attempts to cycle through ten "images" (it never loads the center of the image) by opening/closing ten consecutive windows. In the window's lower left corner there is a box with "St" and then the image creator's name. I have to let it go through the ten cycles, or if I click the window's X in the upper right the cycling stops, before I can use Reader normally. It's really annoying and I'd appreciate any help please.