Are you sure the starter is actually engaging. Sometimes when you turn the key off, an engine willcontinue to turn over for a short time. Sometimes it will be for just a split second... sometimes it may last forseveral seconds.It may sound like it's trying to start, but it's not. It's called "deiseling" because it's firing without any spark.

 

I am new here, but we had a similar problem with our 07 Tahoe. If you put the key in the ACC position and then turned the key to off and removed the starter would ingage and try to start the truck. The dealership claimed something was wrong in the wiring to the igniation. Now we are having over start problems. I posted a question about that earlier tonight.

 

maybe it misses you, and wants to go for a ride