mouse locks and moves whole screen

My new apple mouse does something weird. I must have performed a combination of touches to the mouse that causes the mouse movement to lock. When I move the mouse - instead of moving the cursor on the screen, it’s now attached to the screen and moves the entire screen in the opposite direction. I called apple twice and they were clueless. I’ve looked very long and hard for a settings adjustment that could be the cause. I can’t find it. A restart will release it but that’s a drag. Happens every few days. Any clues? thx