Well, it depends from person to person. I have multiple friends with a panic disorder or anxiety disorder, and each of them experiences panic attacks a little differently. I can tell you what happens in my experience, though even then my panic attacks vary in severity and symptoms, and sometimes are moreso fainting spells than panic attacks. 

I guess I’ll use the one from today as an example. Mine almost always start when I have a migraine or tension headache (which basically feels like a really tight rubber band around your head). To begin with, that makes me really drowsy, because the only way my body knows to cope with migraines and headaches is to sleep it off, since painkillers don’t work. When I’m drowsy, I have less self-control and I feel disoriented, dizzy, and woozy. At this point, I usually sit down, and sip at some water, which works almost all the time if there’s no additional anxiety. Although I wasn’t terribly stressed in choir, we were all standing and rehearsing, and I didn’t want to draw attention to myself by sitting because the music teacher would have asked me in front of the class about it, or just told me to get up (I’m fat so that would cause some glances and comments on its own). So I remained standing, until I realized I really needed to sit down because the world was sort of spinning, and I felt my heart rate escalating because I was stressing about not being able to sit down. My entire body felt hot, my knees locked, and I could hear the warbled sound of the choir singing (I know this sounds melodramatic but this is literally what a panic attack is like) in the background. I felt almost out of body for a minute, then I blacked out. I don’t always pass out during a panic attack, but it’s been happening in the past 8 months or so. If I don’t pass out, I still am unresponsive during the main part of the attack, because I’m paralyzed with stress and adrenaline. Many people mistake my panic attacks for seizures because I am on the ground and shaking violently. I’m not really self-aware, but I’ve been told that my hand especially is jerking around and tremoring. I’ve also been told that lasts a couple minutes. If I’m conscious, I then begin to hear everything clearly, whereas it was background noise and unintelligible chatter before. My breathing slows and I feel exhausted, like I just sprinted a mile. I stay lying down for a few minutes, then slowly sit up and sip some water. Although it’s a little too late now, I take my anxiety medication to sedate me. After about fifteen minutes of rest, I’m very tired and groggy, but I’m fit to move around on my own and get back to class if this happens at school.

Basically, it’s very not fun.