During sleep our bodies temperature drops some so that it makes us more sleepy.
As we wake up our bodies are still a bit colder because our bodies temperature has still dropped some but will warm up as we get moving around.
It's normal for our body temperature to drop some when we are asleep and when we are waking up.
That's why you feel colder when you wake up.
Wearing clothes to bed can make your body feel colder because wearing the clothes to bed makes it more difficult for your bodies sweat and perspiration to evaporate which can lead to you feeling damp and cold.
However if it's cold outside then it's best to wear some clothes such as Pajamas and have a nice thick blanket over you to keep you feeling warm in bed.
Being skinny does make you feel colder than someone who has more fat.
When you're skinny your body can easily get more cold faster than someone who is fatter as the fat person has more insulation which is the fat.
When you're skinny you don't have all that fat as insulation so the cold gets to you much faster.
I'm skinny and I can start shivering really bad when it gets to 50 F while someone who is fat or at least has more weight to them feels warmer in those temperatures.
Fat in your body is a good insulator so you feel warmer than someone who is skinny.
Your body helps produce heat through the use of muscles which help produce the body heat through metabolism.
Our bodies begin shaking when we are cold so that our bodies can warm up.
Although being fat is not always a good thing as being too fat and overweight can lead to heart conditions, heart disease, heart attacks, diabetes and strokes.