Car sitting low over one tire
 

My husband's awesome 2006 A8 has begun to droop over the front passenger tire (and not because I'm heavy!) It only does this when it's parked; when he starts it up it goes back up .... for the moment anyway. No warning lights come on (yet). It has 86,000 miles, if that's relevant.

So what's wrong here and how painful is THIS one going to be?