I experience that from time to time. I kinda figured out for myself though, when it mostly happens, it is usually during late evening. I figured out that I am going too long from supper til bedtime without eating even a snack. I, now, have an apple or something on that order midway to bedtime. That really cured that problem for me anyway. You are right though, you feel just plain cruddy. I felt very tired, a bit sweaty even. I don't really know your eating habits, but if you are not snacking at all in between meals, maybe you should. Even if it is just a handful of nuts. If you decide to try it, I would love to hear back from you. I have learned that by posting questions on this site, someone will reply having had that very same thing, whatever it may be. That is what I love about this site. Take Care, and keep us posted.

mike