when i first take off, there's a vibration under the seats(under the car) that feels like if you were on a 250r (3 wheeler) and put too much weight on the back of the seat making it almost rub against knobby tires. I know that sounds funny, but that what it feels like. And it only happens when i first take off from standing still.

oh yeah this is on a 85 500 sel

sounds to me like the drive shaft center support assembly. the rubber will deteriorate, and cause a vibration like you describe. did you get the PM's and Emails i sent you about the shop in SD you were looking for?

is that bushing , bearing, cap, or boot? or all of the above or???

all of the above, i believe it is sold as a complete assembly, let me know if you need part numbers