I mean serious ones... and the occurences vary. Sometimes I can go 45 mins or so, sometimes less, but the other day it felt like my head was gonna explode right when I lifted the bar off to start benching. I keep myself hydrated. The air-flow in the room isn't the greatest. I smoke weed, but not even within 10 hours of when I workout. I'm currently weening off of it altogether. It occurs in practically any type of activity. It started one day after I pushed myself on the treadmill pretty hard, but it happens when I curl, do leg lifts, etc.... basically anything. It fucking sucks cuz right now i have the motivation and energy, but I think something could be seriously wrong with me.