On the way home this afternoon it became very difficult to shift gears even with the clutch pedal fully depressed. At one point I had to start the engine with transmission in gear and clutch depressed to move. After sitting at idle for a couple minutes everything worked normally. I was able to drive the mile or so on to home with no problem. No signs of leakage. Master cylinder is full and clean. I was supposed to start on a 800 mile trip this afternoon. Any ideas what is happening. Should I risk it?