I had them years ago, around the same time as the 9/11 attacks. Mine started after a friend had a go at me. Would wake up in the middle of the night roasting hot, unable to breathe, with blue lips. Once I could muster up enough breath I'd lie on my bedroom floor to cool down and would end up shivering as I was so cold. Within 20 minutes or so it would be like it never happened. I had to go for physiotherapy in the end. Apparently I don't breathe correctly, breathe from the chest rather than the stomach, which apparently doesn't help. The physio sorted it and I've been fine ever since. If you know of any incident that may have triggered them you need to re-visit any issues from it and deal with them. Best of luck!!