A few nights ago, about 20 minutes after DS (10) had gone to sleep, DP passed his bedroom door and heard him thrashing about. DP poked his head round the door and because DS's breathing was laboured, he came to get me quickly.
DS's legs were spasming, I suppose you could call it, and his chin seemed fixed on his chest and he was breathing very weirdly; not just shallow breaths, but like he was struggling to breathe.
DS has never had a night terror or a seizure before. Although I now know you don't stir a child having a night terror (if that's what it was), because he seemed so distressed, we reassured him we were there and tried to bring him to. We turned up the light and talked to him and gradually his legs calmed down, his breathing became normal and he 'came to'.
His eyes were open throughout and I asked him to look at me if he could hear me and knew I was there, and he did. As we were talking to him, he tried to reply, but didn't make any sense at all; it was just a load of mumble that came out.
Coming round, his right arm was floppy and he was lolling on to the floor - later, he said it was like there was no gravity and he didn't know which way was up. It took him a while to be steady on his feet and to be able to hold a cup of water; on the first attempt, he dropped it on the bed.
Afterwards, he could recount everything that happened; that his legs spasming woke him up, that he felt as though his neck had locked in position, and he was struggling to breathe. He said he felt like he was going to die and was very scared and tearful. 
He was emphatic he wasn't dreaming - said he could remember it all, and that he hadn't been having a nightmare.
We reassured him, settled him back to sleep, and I called 111. The duty doctor said that because DS could recall everything, it categorically wasn't a seizure (I didn't think it was that black-and-white) - but she didn't say what she thought it actually was instead.
And as for it being a night terror, DS could recall the whole experience, and I thought that when a child has a night terror, they don't remember it.
The duty doctor advised us to book an appointment with DS's GP as soon as possible – the first appointment we can get with any GP is next week, so that's booked – and in the meantime, to call 999 if anything like it happens again.
Instinctively, it seemed to me like some kind of seizure, but because of its timing while DS was asleep, we're just not sure. DS is anxious about going to sleep because he doesn't want it to happen again, and I don't want to leave him on his own, so I've been crashing on a campbed in his room.
I'm not sure we're going to get anywhere with the GP, and I've been wondering if any of you in the know have come across anything like this; if you have any idea what we might be dealing with here. Does it sound like a night terror? That's obviously the best scenario.
Thanks so much for any insights/reassurances.