The key unlocks the doors every time but when I try to start the car sometimes nothing happens. Tend to happen only with the newer key purchased approx 4 years ago from Merc in Inverness. The car battery is good and the key has new batteries in it. Also when using this key the steering wheel and seat position has stopped automatically positioning themselves. Does it need reprogramming and if so how do I do it or is it something else? Any help appreciated. Thanks