Your problem started suddenly and you had just filled up, well wait till that tank runs out, then see if it was bad gas. I had a similar problem which I tried to self diagnose on my 83 380sel, changed the ICV, ignition wires etc etc until I took it to an MB Doctor, who said it had a million t hings wrong with it, including timing being off, wrong ignition wires, and few others which were all adjusted. The source of the shaking and rough idle was an air leak under the intake manifold, I am going to get that done nxt week. I don't think that is your problem though, see what happens when you fill up again. Some injector cleaner should also help. ( don't dilute it that much though.)
**A few Hondas etc... etc... Not Worth Mentioning**
83 Euro W126 380 sel Money Pit (Sold)
91 W124 300e 2.6. (Sold) 3.0 Motor is Much better!!
93 BMW E34 Touring Wagon (Sold) Sweet Car!!
91 300e (Just 200k with Ease.)Best car ever ???(Sold)
90 420sel (Black with Tan Interior) Best car ever!!!!!!!