1996 MB C220. Some one has switched plug wires around on the coils. Can you tell me the correct pattern?

For this you will need to know the firing order of the engine, the cylinder numbering pattern and the firing order of the coil packs. Have they removed them at both ends or just at the spark plugs?
Try this diagram for reference. Simply match the numbers. Number 1 on the coil pack to number 1 on the engine, 2 to 2 and so on. You will possibly find the plug wires are different lengths so if they were removed at both ends you might need to swap them around a bit until you get them all correct.
*NOTE* Double check everything BEFORE you restart the engine as this will make sure it starts and runs evenly.

Firing order is 1-3-4-2. You can look at the diagram below to see which wire goes where on which coil.

That can turn out into a complete disaster... look here: http://www.tradebit.com/filedetail.php/116445346-1996-mercedes-c220-service-repair-manual-96

If you need further help, I’m available over the phone at https://www.6ya.com/expert/robert_573a00ba7e399076

Check wire connections if their good replace coil

Coils, wires, plugs, fuel filter. A real tune up in other words.

Before I paid $1500 or swapped engines (nearly as expensive) I would check to be certain the plug heat range is correct, test or change the plug wires, test the ignition coil, check the compression and perhaps do an engine diagnostic.... etc. etc. Incidentally my '93 has a 3.3l.

Should be able to get a new one, can't you? Or call around to the auto wreckers. Should be lots around.

sounds like wiring problem engine harness

The firing order is 1-3-4-2.

buy a chiltons manual at any auto parts store it will have the wiring diagram for the plug wires