This exact thing was happening to my car. From a stop letting off the brake and coasting done a slight hill with foot of the excelerater it would come out of first slight hesitation then slam into second, and also some rough done shifts coming done to a stop. I had a complete trany flush, filter, and conditioner service done at the end of the summer and the transmission shifts are much improved. Were ever you take it I would stay there and watch them do it to make sure you get a complete flush. These cars are a slight pain to do because the battery and tray needs removed to access the lines that get hooked up to the machine then the battery needs hooked back up to do the service then disconnected then re installed (got keep them honest) I think Aamco offering a$100 special on the complete service. Although I don't think I would trust them to do a rebuild but flush maybe.
If you have not had the trany serviced in 71k you are over do
If you have not had the trany serviced in 71k you are over do