About those memories: a human brain is very complicated, beyond our imagination and it can show you or make you feel anything... I know it from my own experience: this summer I spend a month in hospital with serious mental illness. I saw, heard, felt many really weird things and everything was so real - I simply lived for a month in completely different world. But one doesn't need to be ill to realize how powerful a brain is: what about your dreams? They are very complex, you can see, hear, feel - I e.g. had a dream in which I was looking up English words in a dictionary (I'm not native English speaker) - after I woke up I could tell which words I saw there - in alphabetical order!
How does it feel... I also solved this question, but it isn't so difficult as it seems. While you sleep and don't have any dreams - that's how it - approximately - feels. Nothing special. You know: if you can't feel, see, hear etc. anything, you have no senses - you simply ARE NOT, which means that you don't exist within time, space etc. One notice: Why I do think that if you sleep and don't have dreams it's similar to not exist? Because during that time your brain, your senses are very muffled, your consciousness is sleeping (too
)) and so you are nearest the state without senses, brain.