I did observe DS1 breathing at night and witnessed it stop, pause for longer than normal, then restart and a lot of the time the jerking as his breathing started woke him. He'd be frightened and often hysterical with it. He was also a terrible snorer. Sounded like a pig with a heavy cold!
When I finally got to see a GP who took me seriously, he referred him to ENT who said it happened because of his narrow airway and enlarged tonsils.
Following the surgery, his breathing was normal with no pauses and the snoring stopped. However he still has the fear when he does wake up, so he either screams for us or comes running to our room. If we don't wake quickly enough he just gets in our bed shaking and whimpering. We've had endless discussions with him to help him get over this fear, tried bribery, sticker charts, everything. He goes to bed saying he's a big boy and will stay in his bed all night, but every night is up between 1 and 4 times. He was on melatonin which worked brilliantly to get him relaxed enough to fall asleep on his own at bedtime (used to have to hold his hand until he was asleep because he was scared to be alone), but it's made no difference to the night wakings. Frankly I'm on my knees with tiredness and cannot keep getting up to return him to his bed every time (DH is the same), so we put up with co-sleeping part of the night for now.