Ton, Ignition s/w's are a common replacement item audi's. The construction of the s/w is plastic and they are internally spring loaded. Eventually, the spring overcomes the plastice and causes it to crack, thus allowing the switching components inside the s/w to move out of correct alignment. They are rather simple to replace too.
Anyone who can turn a screwdriver can replace one of these. Remove instrument panel (gauges), you may not have to even unplug it, just fold it up on the dash, also you don't have to remove steering wheel, just adjust to furthest-out posistion. Using a flashlight, find back of ignition s/w, unplug connector, and using a very fine sharp slotted screwdriver scrape out red locking glue from the hidden screws on either side of the s/w. Again, using that fine slotted screwdriver, unscrew (DO NOT COMPLETELY REMOVE!) these screws until the s/w can be slid out. Reassembly is the reverse of this process. While you have your instrument panel out, it may be a great time to replace any dead bulbs.
Hope this helps,
Nate