My wife was sitting in line for what she told me was 1/2 hour, but not in park, just idling. She said all of a sudden the car shut off and a hot smell was emanating from somewhere. I read somewhere that GM installed an automatic engine shut off but couldn't find what the time limit may be. I am thinking could also be a sensor such as O2 or Mass Air since it may have been where it was sitting at the time. It started right back up without an issue. Anyone else experience this or something similar?