I dont know how it happened exactly, but it just happened to me.
I went out all day but just had breakfast(maybe didn’t wear enough clothing as well), then I went home around dinner time and couldn’t help shaking. I was aware losing the energy and sleepy. Even putting on down jacket didn’t work, I still felt cold. Finally, cups of hot tea and chocolate and three down jackets saved my life, I was getting better after fell asleep. I survived the losing body temperature. I wont forget this scary experience.