How can I get my iPhone 4S to stop cutting out volume?

It keeps making the volume slide bar vanish. It comes back for a few seconds every once in a while. If I try to connect to my bluetooth speaker it the volume goes on and off because my phone thinks it is also on a dock connecter. I don't even own one and never have. Its impossible to listen to anything at all because it thinks its on a dock that I don't even own.