I have an iMac 21.5 inch mid 2011. The window on the screen keeps bouncing to the side
The page or pages that are open on the screen keep jumping to the side or the bottom or the top. Sometimes it just reverts to the screen with all my most used apps on it. Is there something in set up that I accidentally toggled or what is the problem, please. It is very annoying and distracting.
iMac 21.5″, macOS 10.13