Does the steering wheel pulse back and forth if you put light pressure on it when the car is stationary?
That sounds like the torque sensing mechanism in the steering rack is worn. I've had the same problem to varying degrees in my U12 Pintara, my UA Corsair, U11 Bluebird and I occasionally get a similar issue in my D21 Navara.
I went right through the steering system trying to fix it, but couldn't find a solution short of buying a new pinion from Nissan (between $200-300).
I couldn't justify spending the money so I just put up with it.