Immobiliser /central locking Range Rover Vogue 2002?

After connecting the vehicles battery it will be fine for a couple of minutes but then the central locking will start locking and unlocking by itself without the remote being close by. It will carry on until the battery is disconnected or runs flat. Sometimes the engine immobilizes and it will not accept the EKA code. Battery must be disconnected and left overnight with the hope it get into sequence the next day. PLEASE HELP !!! I'm GATVOL.