Due to its nature of being counterintuitive and situational/stress related, it will present consistently inconsistent. The main thing is to let him know he’s doing just fine (don’t over compliment, just be obviously calm and entertained when he talks.) IF it continues to cause him distress, he definitely could be assessed for SLP services by school or early intervention. But make sure, if he’s given a provider, they are board certified in dysfluency (most SLPs are not and can do more harm than good)