Check the the idler arm bushes, have someone move the wheel while you observe the what the idler arm is doing.............I had a similar thing on my car, the idler arm was moving up and down instead of side to side. In my case I pounded over some curbing in turn 5 and shortly after..........as in the back stretch the car had veeeeery odd steering, exactly as you describe. Basically there would be no steering on the wheel till the slop was taken up, then has the front end loaded up the car would snap turn.

Now of course it could be something else so check all the steering components and all the suspension bushes.

Tom