That was an interesting experiment you did. I certainly have done some 2,3,4 and 5 in my time. Actually the worst case scenario, IMO, is when you want to have sex for reason 2 but then you get rejected and segue into wanting to do it for reasons 3 and 4 because the rejection made you feel needy and shakey about the relationship. But mostly I initiate for reason 1 though I would break reason 1 down into a few categories.
1a) Flat-out physically horny- find myself halfway to the female equivalent of a hard-on for no particular reason as I'm going through my daily routine.
1b) Restless, antsy, cranky and if I ask myself why I know it's because I haven't had sex in a while.
1c) The mind then the body- I put on a sexy shirt or I hear a sexy song or I read a sexy passage in a book or I see my H without a shirt and I start thinking about sex and how nice it would be to have some in some very specific ways.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver