If I start the car, in the beginning I can put in a gear without problems. However, after driving for a while, putting in the gears becomes much more difficult. If the car is turned off, it is always easy to put in the gears. What are possible reasons that might cause this behaviour? The car is already 20 years old and not in the best condition.
Edit: It's a VW Lupo from 2001 with a 1.0 engine with 50 PS.
Edit: Replacing the transmission fluid resulted in a huge improvement :-)