Ignition Problem

[alexanderpaul]

I own a 2005 A6 saloon 2.4 multitronic Audi sport.

Sometimes when I turn the key in the ignition, the car doesn't start.  There is a tiny click sound but this is definitely nothing to do with a battery failure.  I recently took the car into a local dealer who were unable to replicate the problem, so nothing was done.  I also swapped my regular key for a spare one but this has made no difference.  Any ideas please?