You should observe him closely while he is asleep to see if his breathing actually ceases and, if so, for how long, counting by the second
handHand or foot spasms
Hand tremor on your watch. If his breathing actually stops, see if it resumes with a quick, sharp inhalation. There is a strong possibility that he has a sleep disturbance, most likely obstructive sleep apnea (OSA), and will require a sleep study, to confirm the nature of it. At his age, this could be caused by abnormally enlarged tonsils and/or adenoids
(adenoids).