A bike already fits your requirements, self driving would just make it more expensive.
If you want something enclosed, NYC has self-driving (from your perspective) trains and busses.
If you want enclosed and not-shared, I guess you just want a smaller car? Losing wheels wouldn't make it cheaper, IMO, because that makes a bunch of stuff more complicated.
A bike already fits your requirements, self driving would just make it more expensive.
If you want something enclosed, NYC has self-driving (from your perspective) trains and busses.
If you want enclosed and not-shared, I guess you just want a smaller car? Losing wheels wouldn't make it cheaper, IMO, because that makes a bunch of stuff more complicated.