My ignition key started to hang up occasionally so I had the MB dealer here check it out when I took the wagon in for annual radiator flush. Got a call later in the afternoon and the service guy says the ignition swich needs changing. Quoted $780.00 to fix. After I picked myself up off the floor I did a quick search on this forum and presto, found my answer. Ordered a new ignition tumbler with keys and it arrived the next day. Took all of 15 minutes to change it out and it now works perfectly.
Bottom line, this forum saved me big $$$'s. Thank you, thank you, thank you.