BMW 318i e46 locking problem

Hello.

Just recently developed a locking problem on my BMW.
When i lock the car i have to use the key in the lock. I have to turn the key as per normal, not once, but exactly 9 times before the doors will all stay locked. When the key is turned to lock all the doors lock, then unlock themselves until the 9th attempt when it works normally... very frustrating.
Any ideas for a solution?
thanks