Fantail very much nailed it. I just wanted to say that you're NOT alone in dealing with these types of episodes and more people experience them --some to a degree that is debilitating --than you'd imagine. Your body is reacting to what it 'perceives' as a threat with the 'fight-or-flight' response...which is what you'd experience if you were faced with imminent danger. The trigger for this may be a specific situation, circumstance or place or nothing at all. My attacks began 15 years ago out of sleep. I was absolutely convinced I was going to die. I called 911. 20 minutes later I'm apologizing to the Paramedics when they arrive, as I was obviously still alive. After some half-dozen medical workups a very astute MD concluded that I had acute anxiety and depression and after starting medication (antidepressant and anticonvulsant) I was almost 'normal' after two weeks. The doctor and many others have reminded me that not all people will need medicinal intervention; it really depends on the severity. Years later I'm on a low dosage and have managed to keep them at bay. You'll find out that the key to controlling anxiety episodes is exactly what fantail has detailed above: stopping the 'what-if/oh no!' thoughts in their tracks,
breathe and then talk to someone (if you can) and/or post here
In sum, this is not something to feel ashamed or fearful of. Talk to your doctor and a therapist if you can. Realize what your stress triggers are as well---anxiety and extreme stress are quite capable of leaving you in a mental fog and forgetful. It's great that you are aware of what's going on and willing to be open about it.
Please keep us posted on your progress.
All the best!
T.