I'm having similar scrolling issues with Magic Mouse 2 on my 21.5" iMac (2017 model). It's only started doing it since updating to Monterey (currently on Version 12.0.1) My Mac doesn't need to go to sleep to have this issue, it just periodically stops scrolling up & down for a few seconds, whether I'm using Safari, Excel, Word or whatever. The lack of scrolling seems to last for a few seconds and then it starts working again. (Battery level on the mouse is over 80% so it's not low on power). This is really frustrating as I end up scrolling & scrolling with nothing happening, and then it just starts working again. I really hope there's a fix in the pipeline for this!!!