I can't answer the question as to why but I can say that it has happened to me too. Just out of no where they hit. I too seem to have most of my panic attacks at night but sometimes I will have one during the day and I hate it when it happens when I am driving. I had one so bad one time I had to go to the hospital but that has only happened once thank God. I hope you feel better and what makes panic attacks so bad is there is NO explination as to why and where we have them. That's what makes them so scarey...at least for me. Take care and hope you feel better soon.

Little Mouse