Having made a more thorough search of related postings, it seems the areas to focus on are as follows: ignition coil, distributor cap/rotor, overvoltage relay, new plugs, spark wires, fuel distributor (?), and vacuum lines. Once I am up and running, it is quite smooth. I thought it might have been some bad gas but have replaced and still have same problem. Feels as though not all the pistons are sparking together.
I just also noticed that you're confusing engines again.
Your engine, 3.2 liter M104, does not have a distributor cap and rotor. I don't know the proper term, but you have what I call a 'coil pack' that controls the spark. I've never even heard that these go out.
M103 engines have a dist cap and rotor.
The following models share your engine, or a similar version of it:
93 300E / 94-95 E320 (W124 chasis)
93 300E 2.8 (W124 chasis)
96-97 E320 (W210 chasis)
93-97 C280 (W202 chasis)
92-99 S320 (W140 chasis)