Check your tyre pressures first. This would give you very vague steering if excessively low.
What size tyres do you have? The wider the tyres, the more they follow cambers and lines in the road. I had 235's on the front of my Cobra and that nearly caught me out a couple of times.
Also, you say you have checked the alignment, but also check the camber. Your car may have the adjustable uprights and not the fixed ones. So this may cause torque steer and also bump steer.