Shifting Problem, Please Help...

Hey Guys, I am having a problem. I have a 1995 BMW 325IS. It will not shift into gear or if I do get it into gear it jumps when I start the car even if I have the clutch pressed. I know it isnt the clutch. ANy ideas as to what could be causing it, someone said it is more than likely the shift link cable or the shift pin. It has been popping out of gear every now and then before this happened. What do you guys think?