Brian300E,
I believe you have a severe vacuum leak. You could also have a bad fuel pump relay.
The fuel pump relay in my '85 500SEC, is in the fuse box. It looks like black 1/2 pack of cigarettes. The newer ones have a small white filter disk on the front side.
It pulls straight up and out.
Pop the black cover off of it. It may be sealed but you won't harm anything.
You'll find two solenoids(coils inside brackets), the larger of the two is the fuel pump. The smaller is the over rev protection.
Turn the circuit board over and check the support bracket posts on the larger of the two. Mine were corroded and a hairline crack ran around each of the protruding posts. As the vibration of the running engine rattles this crack, the fuel pump shuts off and can re-connect from more vibes. Just re-solder the supports with a little flux and solder.
Also, as the engine's heat and age go up, the vacuum lines become brittle. Check your vacuum lines carefully.
This will help the surging.
Good luck, John F.