This problem started a year ago but in the beginning only less than a minute and only when the weather temp. was low (close to or below 0 deg. cel.). Now is has become much worse and the instruments on/off can continue after start for 10-15 minutes even in quite warm weather. If the car is very heathed by the sun I never have this problem.
dashboard on/off blinking for several minutes after start - cold weather bad on 2000 Audi TT Quattro
Sounds like the Instrument Panel circuit board may be wearing out. I have replaced several in Audi vehicles so it is not uncommon.