It sounds a lot like a vasovagal reaction. I've had them in reaction to pain, drawn out blood draws (it's very hard to get blood from me,) and even to the sight of blood (my own or someone else's, such as when my little sister fell and bit through her tongue). Sometimes I can stop it before I actually pass out, but on 3 or 4 occasions I did faint. Passing out, or fainting make it sound like you just lose consciousness, but wake up fine in a few seconds or minutes, but that's definitely not how I experience it.
The worst was when a phlebotomist drawing blood accidentally hit a nerve with the needle Yikes! My husband said it looked like I was having a seizure - I was flopping around and my eyes were rolling back into my head.
For me, it starts by feeling nauseous, and hot and cold at the same time (kind of a clammy cold-sweats feeling, but my face feels flushed and hot).
My vision will actually go black slowly from the outer edges (a tunnel vision before passing out), and I'll feel like the room is spinning. Then I pass out, and while I'm unaware of what's going on, I've been told I either "lay there or go into what looks like a seizure with muscle jerks and flailing around with eyes rolling. This only lasts a few seconds to a few minutes, and then I start to come around. But it definitely is not just like waking up, fine. It feels almost like I have to "fight" to regain consciousness, and it's very uncomfortable. I hear the voices around me first, and then they start to make sense, and I'm still feeling nauseous and dizzy and it almost feels like someone is holding my head underwater. A cold washcloth placed on my forehead and the back of my neck help a lot. From start to finish it only takes a few minutes, but it feels like a half hour, and it WIPES ME OUT, for hours afterward. In fact, often I have to sleep. After the blood-draw incident, when we got home, I went right to bed and slept for 4 hours!