It’s normal! And a good development!
The most accessible post which covers dozing off quickly and then snapping back to consciousness, is probably one of the first ones u/danl999 made, where he calls it blanking out:
/t/how-to-see-energy-in-3-weeks/131
It happens when the assemblage point is unmoored via your silence efforts, and hasn’t yet latched onto a new view yet.
The snapping back, is then going to be of a slightly different view of this world, a view with a few more emanations which are “normally” not assembled in daily life. Hence the different sensations and or mood.
The books:
/t/booklist/5256