I was a researcher for around twenty years and almost passed out leaning over an LN2 tank like an idiot looking for my samples once. No pain, just felt some tingling and rapidly fading consciousness. There was still a good amount of oxygen in the room since the alarms never went off. Just glad I started to fall backwards instead of into the tank.
I've also experienced nitrogen narcosis while deep diving, and that actually felt good.
Interesting. Not sure if it is at related, but this made me think of the singularly before the Big Bang.