i understand what you're saying as im exactly the same,my body can react and go through the 'motions' but thats all, sex is largely a mental and visual thing so ive always thought that for me its because if i dont have pain/bondage etc the kind of mental and visual stimulation i like then whilst my body is reacting naturally to the physical stuff my head is elsewhere and i have no interest.
i dont find its a problem (unless a partners vanilla lol)and i dont worry about it,it's just the way im wired.
use your imagination ..picture strongly in your mind whatever it is that turns you on concentrate on it and just fantasise and if your partners not that way inclined give yourelf a bit of pain while you'e at it ,it's not quite the same but i used to find it helped a little bit with the vanilla stuff.

sorry not much help just my two pence worth.