When I used to wet as a child, I would usually wake up either just before or just as it was starting. I wasn't a heavy wetter, but more of a regular leaker or dribbler. If I was overly tired or perhaps unwell, I'd be more prone to sleeping through it.
I would usually wet perhaps 3-4 times a week, but as I said, it wasn't heavy. Generally I'd have some sort of standard "pee-dream," where I'd be looking for a toilet or something, and the end result would be finally getting to let go. But mostly I'd start lightly leaking in my sleep, and I'd wake up just as I started to feel wetness.
I know you are asking about being unprotected, but I usually wore thick terry cloth training pants with plastic panties. These were usually adequate to contain my light leakage. Until the age of 10, I wore a disposable diaper on the weekends, as I was allowed to stay up late, therefore making me more tired and prone to a heavy wetting. But it didn't necessarily mean I would wet heavier, but there was more chance of it happening.
But for some reason I would still manage to sleep right through a full wetting during the week while wearing only my trainers, probably once every 2-3 weeks. When this happened, my trainers and plastic pants may as well not been there, as I'd totally flood myself and wake up later in a soggy bed.
Oddly enough, I don't recall ever waking up while totally soaking my training pants, but I do remember waking up while peeing flat out in my nappy, momentarily panicking, then realising that I was diapered and feeling relief.
But if I was just in trainers, I'd sometimes still be asleep in soaked sheets when mum would wake me in the morning, or I'd wake up in the middle of the night cold and wet and have to wake her up to help.
On the rare nights I wasn't wearing any protection, I usually didn't sleep well at all as I'd be constantly getting up to pee "just in case".
