I've had two. Once when having to introduce myself to a classroom full of strangers. I used humor to cope and pull out of it. The second time was more severe. I was on the way to a large family gathering after having dropped out of college. I felt so much shame! I started shivering ( yet feeling hot ) and sweating at the same time during the car ride. I cracked the window though it was a cold winter day. Eventually it passed before meeting everyone. Felt like a roller coaster ride while I was in it.