Mercedes C220 Problem

my first thought would be fuel injectors that are seeping after engine shut down. the fuel pools in intake tract, and when engine starts, the excess fuel is burned poorly - rough running.. once the unburned fuel is gone, engine runs fine.

On older bosch mechanical systems there were enrichment circuits that could lead to the same thing, but i think 97 would be EFI, most likely a few dirty injectors

I would suggest a fuel system additive that is known to clean fuel injectors.

I know... "mechanic in a can" but inexpensive to try...

good luck

let us know how you make out.

JB

Is it smoking heavily during ignition , if it is then you have too much fuel in your injection system, adjust the idling control to regulate fuel. if it is not smoking and the vehicle tends to have low raves then you need to increase the fuel flow to the engine.

I agree with notes posed above on fuel injector leakage into the runner when shut down. This creates a rich cylinder and your 4-cylinder magically becomes a 3-cylinder until the excess fuel is swept through the engine. You should also smell lots of unburnt gasoline and momentarily see some black smoke (at the tailpipe) due to extreme rich combustion during the transition as the dead cylinder begins to come to life. You won't see smoke when a cylinder is totally dead - just air and gasoline vapor which is invisible.

Poor ignition is a less likely possibility (but here are some checks):

1. Also inspect your plugs for severe deposits which can cause a short from the central electrode and across insulator to cylinder head. Clean or even better -change the plugs if necessary. But I'd expect you would see severe problems when you'd open the throttle.
2. check plug wire integrity unless this is coil over plug
3. check ignition coils (need to follow manual)