Do mean a new person in a literal sense or figurative? Waking up after a refreshing sleep can feel like becoming a totally new person.

I don't know where are consciousness goes when we do sleep. Perhaps if we are spirits/souls/consciousnesses inside out bodies, we can drift off into dream world and live a thousand lives then return to our own never knowing the difference.

If you believe firmly that you will wake up transformed into another person, that might be signs of delusion symptoms which does happen to some of us.