e34 first gear problem

[densto]

Hello,
I have a 95 525i with 170k miles original clutch and transmission. Lately I started having problems with my first gear. When I shift in to first gear and let clutch go, car starts to move and then kicks out of the first gear. I am not really technical person so please bear with me.
It does not happens all the time just once in a while and I always try to make sure that I completely shift in to the gear. What could cause this kind of problem clutch or transmission?

Thank you for the help.

[jtw3]

This was also one of my problems with my 90 535i. (see clutch conversion query below). I replaced my shifter seat bushing and it helped alot. Make sure other parts of shifter linkage aren't worn. On my car, the problem is still there but I can feel the resistance going into first and also clutch drag when moving shifter out of any gear at a stop (flywheel problem).
You are correct to suspect the clutch and possibly the trans itself. Hope this helps.
john