if there is no god?

Christianity isn't the only religion touting an afterlife. Even many non-religious but spiritual ideas touch on it.

Personally, everything else in the Universe is a cycle, so I don't see why our lives would be any exception to this rule. I think the ones touting reincarnation are closer to the mark, although I doubt this is instantaneous, and there is likely some duration of "being" in another form between incarnations....