Ive had it before, its bad to where the mirror isnt usable which is a safety concern.My 22 does this too. Its a mustang not a caddy deville. Shits going to vibrate and make noise.
I just did this on my 2019 A10 PP1 with some suspension/brake mods.I had a similar problem on my '15 ragtop. I found that the set screw that attaches the mirror stalk to the windshield was loose. I tightened it up and the mirror is much better. It's worth double checking it. I'm pretty sure it's a torx bit.