2012 Mercedes E350 4 Door sedan will throw itself into park at crawl speeds.
My Mercedes E350 4MATIC has a weird intermittent issue where when I slow down to a crawl or almost stop, the transmission completely freaks out and rapidly cycles through D/N/R/P before violently slamming itself into Park. Every time it happens I have to manually put it back into Drive to move again. No warning lights, no flickering electronics, no radio resets, and the rest of the car works perfectly normal including brake lights. The car was previously sent to a mechanic for this exact issue and they found the auxiliary battery was low/dead and replaced it, which actually fixed the problem for a while, but now it’s starting to happen again. Main battery also tested fine during inspection in March. Trying to figure out if this sounds more like a conductor plate, speed sensor or shifter module issue or if the transmission itself is starting to go.
Any help would be appreciated as I am a broke college kid who doesn’t have the money to spend looking through codes and things just to maybe find the problem.
Edit: The engine is a 3.5l V6