Sticking Speedometer 2003 Nissan Pathfinder

I recently bought a 2003 Nissan Pathfinder and find that the speedometer sticks sometimes(45to 70ish mph) until either I slow down considerably, speed up considerably or tap on the class over the instrument panel. Example...I am going 55....I slow down but the needle still points to 55. Finally after a little bit it "breaks" and swings down to the speed I am goin. Does anyone have any ideas? Thanks in advance.