I see "reasons" to jack, their little furry and have long tails. We are not as cosmopolitan as Frank, our FX stays jacked up and covered in an old cold garage, along with bikes, snow blower, mower and all the other crap garages have. We put mice traps around the base of each jack stand and there have been a couple sprung with a dead body.
Frank your car seems OK now? Gary said a way remote idea is fluids settled, rough vibrations getting everything back and moving around correctly again...he said remote idea. He though the cold tire idea was much more likely. Hows the new mufflers??