This is not a hangover, this is not the result of sugary drinks, it is not the result of eating/not eating. I have this exact problem, and no one knows what it is. I don't even have to drink enough to be drunk, I can be completely sober but when I go to bed or start to fall asleep, I will shiver and shudder. I often have to make myself throw up to get it out of my system and to let myself sleep. It DOES feel exactly like an anxiety attack, but like only in your body! Like mentally, I'm totally fine! It's my BODY reacting! I know exactly the feeling you are talking about, and I am considering seeking medical attention because it IS really annoying and makes it no fun to go out with friends. I don't want to drink because it makes me feel like ****, but no one gets that and I end up getting pressured all night. Please don't minimize your problem because it's real!!