Sharon, that does indeed suck. What was the tech's recommendation? I know you're tpissed and arm-chair quarterbacks like us will not help you feel better, but heck, you deserve to have a car that runs like a new car!
Don't give up the fight. Contact your local omnisbudman that helps people with these kinds of consumer issues. No doubt, Chyrsler does not want bad publicity about their products and service. Take it to the Mercedes dealership and keep all your receipts and inform them of your saga with this car. Perhaps they can clue the technicians at your dealership.
I thought they had assured you that the car would be fixed or replaced. You have a problem that is definitely safety related and that fact alone is reason enough to stay in their face about it. I'm so sorry!