on a K11?
...I'm not sure...
My K12 does...after about 5 minutes (if you haven't opened the boot or any doors etc)
...there is an easy way to find out of course...get your coat on and see if it locks itself again
ETA: I only discovered this when I was leaving work one night and stood chatting to my colleague for a few minutes after I'd unlocked the car and then I heard it click locked... ^_^