Just thought sharing my own experience might be useful.
I found on one occasion that my car ('97 A8 4.2 Quattro sport) didn't want to let me move the lever out of 'park', even though I had my big foot on the brake pedal. I switched off, then back on and away I went as normal.
A week or two later it did it again but this time it took me a minute or two of skiddling around, switching on and off etc before it would go into drive.
Went home and decided to fix it.
If this happens to you, get a friend to check if your brake lights are working properly. Mine were not, so plainly the car was not 'seeing' me putting my foot on the brake and therefore, correctly, prevented me taking it out of 'park'.
I dropped the trim below above the pedals-only took 10 mins and I've not done it before. Found a loose wire on the brake light switch.
Problem solved and no trouble since.
