ONLY DO THIS WHILE CAR IS COLD!!!!
It's your power steering fluid needing to be bleed.
To do this remove the power steering cap, Undo the belt of the power steering pump, Turn pump clockwise constantly for 2mins+,
Get into the car and full lock the steering wheel right and then left,
(I put mine on a trolley jack to get the weight off the wheels)
Put wheels back into the straight position, Turn the pump wheel for another continuous 1min+,
Then put the belt and power steering cap back on and start the car and this should eliminate the shudder,
If it's still there repeat the process