Unwelcome & frequent expansion of the monitor image and pages.

I had an old 2017 iMac 27 inch that suddenly started expanding the image on the screen as if I had clicked on the 'command' key + the '+' key. It was doing this all by itself. I could get the screen back to normal size only by putting my cursor at the end of the top task bar address and clicking on 'return'. It kept doing this on occasion.

I then updated my computer by purchasing a new Mac Mini M4 and migrated my stuff from the old iMac to the new Mac mini.

Unfortunately, the bad behavior also migrated to the new Mac mini and my monitor screen continues to enlarge on its own requiring me to repeat the actions described in the first paragraph of this question.

I have Bitdefender for my anti-virus and I ran a complete scan. No viruses were detected. I performed 'First Aid' with my disc utility and the Mal-behavior is still happening.

Are there any knowledgable recommendations out there to remedy the problem?