The story I recall is told from the point of view of a protagonist who wakes up every day in a different person's body. Always a man, always in the same city. He does not have access to his "host's" memories, but muscle memory sort of works. So if he needs to open a door, the body will start to move to get keys, that kind of thing. As a result he tries to avoid interacting with people who know the person. If someone tries to talk to him - his host actually - he will try to dodge them or make an excuse to leave.
He almost never tries to live any of the activities in the life of his host. He just gets up, leaves wherever he wakes up, and does his own things. He has a locker that he keeps his own stuff in, and he often spends time at the library.
He comes to the realization that not only is everyone he is inhabiting the same age, they were all born in the same city. So he suspects that he - whoever "he" is - must have been born then and there as well.
One day his host is a doctor, and this time he actually dresses as the doctor and goes to the hospital. He finds a man, the same age, comatose. He has been comatose for years, maybe from birth? Perhaps there was some kind of accident or event? But the comatose patient's brain always shows a certain amount of function, as though it were continuously forming memories...
This last is much less clear, and I may be conflating another story, but I remember that his (the patient's) father may have been doing experiments on him. As in, inserting tubes into his head and extracting a portion of his brain each day. So the ability to use the brains of others around him was an adaptive trait from a desperate attempt to survive that.
It feels to me that this is something I probably read in Analog in the early-to-mid 90's.
