My 6 Year Old Beagle Is Panting Quite Frequently Even

My 6 year old beagle is panting quite frequently even though in an air conditioned house all day. She was also shaking last night as well as panting. She is very restless, keeps going to the door wanting to go out, and can't seem to get comfortable on the couch. Lays still for 1 minute then moves to other end of couch.