I Was Curious About What Might Be Causing A Slight

I was curious about what might be causing a slight head movement that goes back and forth. I could be reading , driving, watching TV or doing anything and then realize it is moving back and forth. I consciously make it stop and then later I notice it's doing it again. It's annoying, but causes no pain. I talked with my Dr. a few years back and he said it was caused from old age. Would you give me a better idea if I should be concerned? Thank you!