Definitely not normal, haven’t noticed any seat movement in my A4. I’ve put about 7,300 miles on it since August. I did have an Acura with a “loose” passenger seat. I believe the dealership replaced the tracks. Repair was a success, but then noticed the seat visibly vibrated at highway speeds. I bought it CPO and still wonder to this day if the seats were intentionally loosened to hide the visible vibrations. Had wheels and alignment checked and it still shook.