Michael and yal both made good suggestions. I think I would move the tire myself, because tires are probably not covered under your warranty. If they were to do a lot of work and found that it was the fault of a tire, you would be in a bad situation.
After ensuring that the tire is not the problem, take Michael's advice and call the regional MB representative. Be persistent and don't take any nonsense. I went through an intermittent problem with an M-B dealer once. It only showed up occasionally, I finally got the regional rep involved who had them drive the car until the problem showed itself. They fixed it. Had I not gone over their heads to the rep, I would never have gotten any satisfaction from that particular dealership. I believe that most dealers will be persistent and find your problem. But there are a few who just want to make some flimsy excuse to get you out the door so they can go home to supper.
Check the tire and then don't take any guff. I'll bet you worked hard for the money you paid them, occasionally they have to work hard to satisfy their customers. Life's tough.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in