shutter problems on pentax ME

I just bought a used pentax me. When I took some pictures the shutter worked properly on the first frame , but then the shutter seemed to automatically operate when I advanced the film.I did this for a few frames and then took out the film.It still did this a few more times then began working properly again. I am reluctant to put more film in it before I know whats up. Also I think the batteries are going dead. Don't know if that matters.
Please help. :confused:

I have since noticed that this only happens when the lens is fully mounted to the body. If the lens is unlocked and turned slightly just enough so it does not lock, it seems to work fine. Is this a problem with lens or camera? :confused: