Welcome to the forum Mike :)
You'll find the members on here are a friendly and helpful bunch :)
Firstly have you had a diagnostic check carried out? If not then I'd say this should be your first port of call.
The Quattro system is great but can also be sensitive to changes in the car which can cause damage to it. For example uneven or mis-matched tyres, worn suspension parts or bad wheel alignment.
Sorry I can't help more though.
Cheers
Steve