There are a number of songs, films, and other cultural artefacts that use or reference this term, but I can't figure out if it has some kind of idiomatic meaning. Any ideas?
The literal meaning is obviously moves that are made at night, as in the lyrics of Bob Seger's song of that name, the specific kind of moves there being sexual ones. But the earliest of the cultural references (listed by Wikipedia) is the 1975 film with that title, and it's reasonable therefore to assume that this is the origin of the phrase in popular culture. In that film, the title is clearly a pun on 'knight moves', since the central character is interested in chess. The knight in that game is the only piece that is capable of jumping over another, so a 'knight move' might be understood metaphorically as some action that is on a different level to those made by other players; or alternately, as one that goes round corners when all others must travel in straight lines, since that is also a characteristic of the chess knight.
Another possible meaning is from the military's habit of moving positions under the cover of night. During my own military career it was a necessarily common (although loathed) training exercise to move to a new position during the night. These exercises were frequently also literally called "night moves".