What causes an emotional feeling of floating when first waking up?

I tried google-but it told me I was dying. So, I thought I would ask here.

I am open to any guesses, but I am hoping to figure out what is going on with the neurotransmitters in the brain.

I can recreate this feeling with meditation. If I go into a deep meditation, when I "rise back up" to awareness- this floating feeling appears.

It seems to clear on its own, as more parts of the brain "come back online".

It is a pleasant, drowsy, contented, floating feeling. Like waking up in the middle of a cloud where the possibilities are endless.

What are your thoughts?