I had this problem on an 87 300E one time and it was the fuel pump relay. It has a rev limiter in it. The customer, thinking he was fixing a no start problem put in a fuel pump relay from a 4 cylinder 190 or something. It fixed the no start problem but he later found this problem. Replaced the FP relay and fixed the problem. By the way, most of these relays have are marked as 4 , 6, or 8 zyl. Could also just be a defective relay.
84 500 SEL (307,xxx miles)