Notchy steering wheel while driving

While driving at average speeds, when the steering wheel is in a neutral position, the wheel seems to
fight me when I try to make small adjustments in direction. It is not smooth. I'd describe it as notchy in
this position. But this doesn't always happen. Most of the time, there's no problem at all, but I imagine
that it isn't good that it's going on at all. What is the problem or what should I do? Thank you