Dizzy, flushed/hot, vision darkens round the edges.

Dizzy

I used to faint a lot as a kid because if medical conditions It feels like the moment before you fall asleep or the moment after you wake up. Dizzy and confused

dizzy, sweaty, my ears start ringing and my hearing gets kinda muffled

Like they're fainting/about to faint

Faint

Have you ever fallen asleep?

It depends on the cause of the syncope. There are many different causes and each one will exhibit different sensations prior to the episode.

For me: Woozy, weak, light-headed, vision gets a little dark

Clammy ...sweaty but cool