Why won't it go into reverse and sometimes I have to move the shifter to start

Hello, I can give you the bad news, is that this is very likely an internal transmission issue. There is another chance, and that is an issue with the shifter, linkage, or transmission electrical system. In either case, there will need to be some disassembly for diagnostics, and that may be interior parts or transmission components. If you have other questions, or need more information, let me know, otherwise, here is a list of certified shops in your area with the training to repair your vehicle: http://repairpal.com/mercedes-benz-within-10-miles-of-tulsa-oklahoma-74107