Not all that infrequently (though not in the last week iirc) I find myself in a state which I think of as being, “half asleep” (or (3/4) asleep, or whatever. Various degrees of “asleep”) and I’m still able to kind-of think about things, but such that it is easier to accidentally forget what I was thinking about, such that I’m not able to keep as much in working memory, more distract-able by random thoughts, etc. . (On rare occasion I find my breathing while in this state to be concerning to I get scared and wake myself up. I’m pretty sure it’s been over a year since that last happened. I think it was mostly when sleeping face down or something?)

I suspect the type of state I just described (not the breathing part) is something most people sometimes experience. I don’t think it is unusual. Though I don’t think I’ve often heard people describe it in detail.

Does it seem plausible to you that you were perhaps, “20% asleep, but 80% awake” during that time?

Edit: also, my understanding is that lying still and resting can work as a partial imperfect substitute for some amount of sleep (though not like, in a way that can be sufficient long-term)

You appear to be describing https://en.m.wikipedia.org/wiki/Sleep_paralysis

no they don't.....

Sounds a lot more like this: https://en.m.wikipedia.org/wiki/Hypnagogia

I'd recommend getting a super cheap camera that can record yourself sleeping. You might have actually been asleep (according to this article).