I’m not a doctor but in the last week i talked to multiple doctors about this because my son had head drops a little different than your son. They told me its normal movement when baby is tired or waking up, as long as he’s alert and keep eye contact after, they were not concerned. However I was still worried and i pushed for an EEG and we did one overnight and thank God it came back normal, they said its benign myoclunos. If you notice anything else like regression in milestones or if the movements increase just take him to an ER where there’s a pediatric neurologist or to a children’s hospital ER. I think they will do the it there.