I have a 2011 Acadia and earlier this week I was getting ready to leave for work (in our other car). I noticed the tail lights and the the head lights come on in the Acadia. I looked inside the car and noticed the keys were left in the ignition (in the off position) . As I got ready to open the car door the car started on its own. We only have 1 key for the vehicle and that was the key inside the ignition. I turned the key forward and then back to the off position and the car turned off. I do have a factory automatic starter and the car door was unlocked so they automatic start should not start. Does anyone have any ideas?