Steering Sticking

When i bear left on a large left bend leading to the motorway my steering/tyres feel like they get stuck and i have to readjust the steering as it feels like its kinda gonna go back on itself. it also does it whilst im driving on the motorway on a straight. its like it jarr's and sticks a bit...really difficult to explain
iv had it in the audi garage for a check and they said that there was nothing wrong with it. it isnt the tracking as that is also fine as well as fluids etc.
i have had this car for over a year. For the first 12 months i had the car it never did this once. then one day it stuck slightly and since then it hasnt stopped and is getting progressively worse. :1zhelp: