Death -- I think. Not knowing what death feels like i would assume that anesthesia feels the same in that you feel nothing. You have no sesne that time goes by. There is no dreaming during anesthesia ( sometimes you may have dreams from other drugs used during the wake up process but not during anesthesia.) you simply close your eyes and then open them a half second later. But it's later and in another room.
Drowsy. It is like gradually falling a sleep after taking sleeping pill.......
Very Few Know. With modern anesthetics we try and shut down the memory of the patient before they go to the or. Once they can't remember what happened, it is very hard to find out what they felt as they went to sleep. Without sedatives the very medication that is used to put people to sleep blocks memory formation, so we have the same problem. Same with waking up. Patients come to in the pacu after the op.
A relaxed sleep. You drift off to sleep. As was already said there is no sense of time or sleep. You wake up at a later time in a different room.