Imagine relationships are non linear and you could choose where you "started". Where would it be? Would you go straight to sex? Get the break up (if there were one) over with first so you'd know you'd have nothing but good stuff ahead?
I think I'd start before sex, but after the first part of figuring out how interested you are in each other, in other words we'd already have figured out we were interested in pursuing a relationship or just sex.
This is of course assuming a classic/average relationship of coffee, dinner, movie, sex, intimacy, love, marriage, kids, divorce or death. Obviously not all relationships will last, and some might start with sex, or are missing love or whatever. I suppose this might reflect on if youre one of those people who reads the end of a book first.
I don't think I'd want to know the end, but I'm impatient in the beginning.
Hope this makes sense.