2000 Expedition with 63K miles has started acting up only when cold. Starts fine, reverses out of driveway, and then when shifted from reverse to drive, revs and hesitates before moving forward.... Is also stalling occasionally, also when cold, when pulling out after a stop. Had the 60K service performed several months ago which included new transmission fluid. Temperature here in Alabama has just recently gotten cold in the morning. (50-60) Took it to the shop, but no trouble lights, nothing in the registers, and won't repeat there... They say they don't know what to do.

Any ideas?