When I first had them I didn't know what they were. I was under the care of the eating disorder team and talked to the nurse at my next appt, and she told me that's what it was.
I had just come out of an abusive marriage and was starting to unravel everything. I think the 'safety' of being under the care of professionals allowed my brain to start to deal with things.
Physically, they stopped me in my tracks and I felt tingling wash over me. My breathing became rapid, my heart beating fast and my hands sweaty. They were triggered by memories and flash backs of my past and would hit me very unexpectedly. They didn't last for long, but left me very unsettled for a while afterwards.
One particular episode happened when I was away on business, fortunately not working at that moment, but out for a walk. I remember feeling that I just wanted to get back to my room, but don't really remember that walk back. Now I would know what was happening I would be able to manage it better.
What helped was 1) knowing what they were 2) learning grounding skills (focus on breathing steadily, telling myself I am OK, that I am here, safe in my home) 3) just going with it knowing it will pass.
I still get the feelings, but rather than a full on panic attack it's more a high level of anxiety that I can manage. It's still unsettling though.