It could be the fluid filled moter mounts. They need to be replaced at around 60K Miles. They start leaking fluid around this time.

 

I JUST HAD SAME PROBLEM. I TOOK OUT PLUGS AND FOUND ALOT OF CARBON. LOOKED AT COILS AND FOUND CORROSION INSIDE TERMINALS. ORDERED TWO COILS (90) FOR BOTH ON EBAY(DEUTCHEPARTSUUSA) AND GOT WIRES AT LOCAL FOREIGN PARTS DEALER. HAD PLUGS IN, COILS CHANGED AND WIRES DONE IN LESS THAN AN HOUR. THE MB DEALERS ARE THE CLOSEST THING TO FRANK AND JESSE JAMES I'VE EVER SEEN! THEY CHARGED ME 780.00FOR A NEW AIR MASS SENSOR LAST YEAR. YOUR 600 DOLLAR JOB COST ME 140 AND AN HOUR'S TIME. CAN YOU IMMAGINE THE PROFIT THAT GOES THROUGH THE MB SERVICE DEPT EVERY DAY.