A bad problem in mercedes. I have 3 and all 3 have had to have the ignition switch replaced. My 190e 3 weeks ago. I usually do alot of the work myself but that one I wont touch. Call AAA and tell them to send a tow dolly truck and surely there is a former Mb dealership mechanic around. new switches only come with one key so you better ask them to cut you a coupke extras. About 350.00. The part is about 130.00 and 2-3 hour labor.

1983- 300DT-439,000 miles
1991- 300E- 371,000 miles
1991- 190E- 172,000 miles