car is slipping out of gear into apparently neutral while coming off acceleration and can only be corrected by restarting or slowing to ten miles per hour or around that number

Sounds like your transmission is slipping. Chances of stored codes that could be read are good. That transmission can be rebuilt or your can get a rebuild trans from MB directly. Due to the high torque produced by your engine and usually poor maint (MB says lifetime fluid) causes the clutch packs to slip.