Sleep Paraylsysi: Awareness shift

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I am wondering how exactly the awareness shifts, I remember when I was so tired, I kept counting to like a 100, but unfortunately all I got was nothing, I heard repeating your name, and when your attention goes to other things, to keep repeating the number/name/etc. Like I had stuff pop in my head that was totally random, and then I was like, how the hell did that come in my head? My question basically is, how do you feel right before this state, Emotionally, Physically, etc Also I sleep on my side with on leg straight and another leg like a v