All programs responding slowly or not normal.

My iMac started acting weirdly, at first with the mouse not working properly. It was super slow.

Rebooted and reset the settings on the mouse and now appears to be working properly. Then my programs started to acting weird. Quicken wouldn’t work properly; couldn’t enter new transactions. And then my google sheets kept wanting me to copy/paste whenever I tried to type numbers into a cell.

The entire computer is acting very strange not allowing to open or close programs.

Any suggestions?