2010 GL550 40k mi. shut car off in drive and now wont start

Hello, The transmission is supposed to put the vehicle in park the second you remove the key. Funny enough, I have an ML, and I have never put it in park when getting out. I just let the car do it for me since there is no difference to the operation. If the transmission is stuck in D, even when you turn the key on and try to shift it to N, the shift motor or position sensor is likely bad. However, that would be a coincidence since it sounds like you often place it into P. So I wonder, does the gear selection readout say it is in P, D, or N? Did you hear the transmission shifting to park like normal when you exited the vehicle?