If this behavior corresponds to the weather, you might try removing the steering damper and checking it for binding. Also try a drive without it for comparison. If moisture got past worn seals, it could be shot.
If that isn't the problem, I would jack the front tires off the ground, and preferably support the car under the lower control arms. This can be a pain to do, but allows a similar geometry to driving for testing some components. In particular, check for rotational friction that comes from damage or wear to the strut or lower balljoint. This is easiest to do if you also separate the tie rod ends. With the ends disconnected, you can also check the centering friction of the steering box (engine off).