8mo tilting head to side with what could be involuntary nodding/bobbing. just exploration? teething? or something more concerning?

All or nothing: Could be all of those things or nothing other than habit. Could also be hearing impairment. Please see your child's Pediatrician. And when your child turns 1, take him/her to a Pediatric Dental Specialist, a Pedodontist, to begin a lifetime of optimum oral health.

Mgt: I would suggest reviewing his growth, head circumference, development and findings in detail with your PCP. An inbox consult may also be helpful.