my car just spontaneously started then stopped....in the garage

Spontaneously means to act without external cause. Are you saying the Terrain started on its own, then shut off? Or did you start it, it started then died? You may have a computer chip issue. That needs to be tested.

starts on it own

My 2019 GMC Acadia did this last night. Started on it's own woke us up, my husband had to go out to the carport with my keys that were hanging in the kitchen and turn it off. I googled it and this is the only thing I could find like what happened to us

2010**

This just happened to my GMC 2014 too, we were no where by the keys and it randomly turned on in the garage, we had to put keys and and press break to get it to shut off.

Anyone ever find a solution to this? My 2011 gmc acadia just did the same thing last night

My 2014 Terrain does this all the time . Turns on and shuts off by itsself. It usually never stays running for more than a few seconds. Sometimes it will do it so much it drains the battery from trying to start itself or has the wipers n flashers all on ... dealer said it was a bad battery n put a new battery in for $300 . Still have the problem...

Has anyone out there ever had a diagnosis or solution to this problem. My 2013 Terrain does this and I'm about to drive it into the lake!!

My 2010 terrain started doing this