Asthma. People expect you to have dramatic TV style throat closing episodes where you turn blue grabing your throat as you gasp and gag. For me, an episode is just sudden onset hypoxia. I'll feel my lungs get tight, but because I'm still getting some air it can be hard to tell I'm suffocating, especially if I'm distracted. When it happens, I have about 3 - 5 minutes to catch it. If I fail to catch it, I'll quickly lose balance, struggle to speak, I'll be unable to think, and finally my vision darkens to a dot, and then I black out. I can appear fine, and then out faster than anyone expects.
Once I get a puff, I'm fine in 10 seconds (minus some shaking from the medication.)