Has the child had a recent MRI or app't with the pediatric ophthamologist? Head tilting could very well be related to vision issues. Head tilting can be like squinting, a coping mechanism to improve whatever is going on (strabismus, double vision etc). Kids can also pick up all sorts of temporary gestures but I definitely would have it checked out asap.
Hoping it's just one of those things. Keep us posted.
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