Wobbly rear view mirror.

Over the last few weeks, my rear view mirror has become more and more wobbly and has lost most of its rigidity within the ball and socket joint. When I drive along the view out of it is distorted most of the time due to the vibrations travelling from the wheels upwards. The car is going in for its first big service in two days time and I've asked them to look at it. I haven't knocked the mirror since I've owned the car so I have no idea how its got to the state its in now, but seems to have deteriorated since the hot weather bestowed itself among us.