What Causes Pain In A Child Neck On Turning?

my child is 3 and has already had an x-ray on her neck and everything came back normal. Here the past couple of months though she can be doing much of nothing and I can't hear it pop but she gets a pain in her neck, just by turning it sometimes. This seems to happen a couple times a month. I have set her up another Dr.'s app. tomorrow but they say they can't understand it either. She has had no accidents and it just started a few months ago.