Relationships (and sex lives) work well when both partners are invested and willing to make it work. It sounds like, at least when it comes to sex, that your partner isn't invested in making your shared sex life work. Or at least the two of you haven't found a way to address whatever is getting in the way of having sex together. I don't know how the rest of your relationship is going, but it may be worth some serious conversations about what the two of you each want and whether you are still good together. As for your partner getting you turned on and then disappearing, that sounds like a power play or punishment and is totally in bad faith. Challenge them on it--if there is a problem to discuss, then they should bring it up but that you aren't going to take the bait any more and respond to their initiations unless they are genuine. Unless they don't think you'll leave (and that may be accurate) they are playing with fire with those kinds of moves.