First off~ do not panic (after reading the previous post)...
I also go to bed cold, dress in a t-shirt and flannel pants and wake up sweaty. However, I also have a bunch of bed layers and I burrito and cover my head~ :)
I have found when I am stressed out of my mind (as I am this week over some things with my son's school)... I wake up sweaty. I also wake up that way when I am fighting a bug/ virus. (which can be for a few days).
Let me also mention that I use a spare heat pad (for a massage table) on my side of the bed and I do not always sweat with that when it is on, either. It is only from stress or fighting a bug. Sometimes I know I am warm, and shut it off, and still wake up soaked~ (but I use this as I do have Rheumatoid Arthritis and the heat helps my joints by helping to eliminate stiffness.).
If you are overly concerned and this has carried on for over a week~ check in with your doctor. Chances are it could be stress or diet. Sometimes even certain foods we eat can cause us to detox that way. (At least it does for me.).
Just remain calm and try not to worry to much. :)
EDIT: OH~ and make sure that you counteract this by drinking more water to rehydrate yourself. I find this to be a cause of some of my migraines when I do not sufficiently replenish my water intake (I always have a big glass of water by my side all day and on my night stand for when I wake up in the night time.)