I have recently experienced some sort of tapping noise on the left rear of my '90 300CE with 148K miles. It only occurs upon acceleration from a stop, and is quite noisy. Once up to speed, I no longer hear the tapping or knocking noise. I got under car to see if the muffler hangers were broken, or something obvious would be visible to this novice. No such luck. Anybody have an idea? Thanks in advance.

Mike