Audi Repair Questions? Ask a Mechanic for Answers ASAP
Can you shift through the gears with the engine not running? It sounds to me like your clutch is worn put.
So if you put it in a gear, depress the clutch and start it, does it feel like it is dragging, like the clutch is not fully released? Does it drive OK once you are moving? Have you tried powershifting it while driving, without using the clutch (matching rpms and sliding it into gear)
Do you drive with your foot resting on the clutch pedal, ready to shift?
Have you checked the oil level in the gearbox? I can't imagine that a 5 year old car has a leak, but the time issue seems to indicate that something is warming up to the point where tolerances get tight or something similar.