transmission will not engage or change speeds unless I turn the truck off and restart! why hasn't there been a recall?

Certainly, you could get with your Mercedes-Benz dealership local to you and express your concern. However, "recalls" are issued for certain safety related defects in compliance with NHTSA (National Highway Traffic Safety Administration). Simplified, a certain amount of data and vehicle owner concern reports have to be collected, and evidence of a defect needs to be compelling to create the need for a safety recall. Certain manufacturers will also issue "product improvement" campaigns based on feedback from vehicle owners, potential litigation,and owner loyalty defection risk. Even with the Internet with sites like RepairPal and other forums where folks can express concerns about vehicle issues, it doesn't necessarily indicate a "consensus" of failure of the operation of the transmission of this vehicle. All that to say: consult with your local dealership to express your concern. Maybe they would be willing to assist in some way. Honestly, with a 10 year old vehicle -- unknown to me mileage -- it's going to be difficult to get assistance, but worth a try. Good luck.