Is it possible that someone could be hyperventilating when nervous and not even realize it? if so, how does this work in the body?

Fight or flight: When we come under threat or feel nervous our fight or flight response kicks in heartrate and respiration rate increase and along with a narrowing of vision or focus on the threat we can become less aware of our breathing, only making it all worse - the classical cure for that is taking some long deep breaths, holding, exhaling slowly, holding, long deep breath.