Rookie
Sounds like a touch of good old orthostatic hypotension. I get it all the time, especially if I've been squatting for a bit and then stand up suddenly. Luckily I've only passed out a couple of times, and I've learned how to minimize its onset. I call them greyouts because one's vision gets grey around the edges and the field of vision shrinks.
I hope it happens more often, so that we'll be compelled to figure out a good way of dealing with it.