Stetson Call

I know my car (w212 E63) came from the factory with a keyless start, but what safety features does it have? Say I go outside and start my car in the morning to warm it up before I go to leave and left the vehicle running with no fob in it can someone hop in and drive off? Most answers I've found aren't very straightforward. I've heard some yes's and some No's and some other things like the car will not allow you to put it in gear with no fob. I havent really had the time to test it myself im always busy, so I figure someone in this forum should be able to provide an answer... Its just kinda concerning, the thought that if it allows the driver to drive the vehicle without a fob; it could very easily be stolen... figured id see what yall have for me