rpm's S2

My clutch is refusing to completed return after each shift. It is disengaging, just staying about halfway up each time. I can pop it back up all of the way with my foot. This seems to have started about the time the temperature dropped a few weeks ago. The problem subsides after 20-30 minutes of driving.
Any ideas? Is this a lubrication or a linkeage problem?

MAS

It's likely that the clutch master cylinder needs replacing. That's a classic symptom.

-MAS