The central locking on my '87 300SL spuriously turns itself on and off both when driving and when parked. I have played about with the system by connecting/disconnecting the wires to the control box in the boot. Through this testing work I think the problem lies in the wiring to the drivers side door mechanism (the door switch itself has been replaced - no change).
It does seem to be worse if the weather's wet whcih may suggest an earth fault somewhere.
I do not know the routing of the wiring from the control box to the door or whether there are any well known problems with this system. The car did have an alarm fiited by a previous owner that connects into the central locking system somewhere but this never worked well so it has been unplugged but not removed completely.
Any guideance would be welcome.