It could definitely be linked to a medication, especially if it is a med for ADHD or some type of stimulant. Stop any meds immediately and wait 4-5 days to see if it ceases. It can also be hypo or hyperglycemia due to glucose levels. Check this
Children typically do experience night terrors, myoclonic jerks, and tantrums. Rarely are these symptoms of anything else such as rare side effects of Singulair or conditions like Tourette's or seizures.
I have read there could be underlying illness from the description you have given, tourette's or epilepsy. Also, you did not mention if any meds have been introduced.
I would suspect foul play. If he is left with others to care for him at all I would immediately withdraw him and seek psychiatric counselling to rule out abuse.