Although it doesn't do it all the time, every once in a while my speedometer needle jumps between speeds. Like it will be smooth accelerating from 0-10 mph, then stop, then jump up to like 25 mph, then pause... all the way up until I stop accelerating. It never does it while I'm braking, only while accelerating.
oh ya, and I've noticed it does it alot right after I get off the highway and get back into the city...
sounds dumb, but is the needle itself lightly touching the faceplate of the speedo? i know the exact thing happened in my 97 sl2, and all i had to to do was remove the clear plastic shroud and gently pull the needle out maybe 1/8th inch.
either that or it's your speed sensor which cost a million dollars and you'll go into debt and your parents will cut you off and you'll hate life forever.
actually i think the sensors are like 30 dollars..
jumpy speedometer 
Linear Mode
