I think the other posters have good points - it sounds to me from what you say that your W does like sex and want you, but perhaps the way she communicates it is more subtle. The gap between "willing" and "wanting' can be just a few minutes. Unless her "willing" has an undertone of resentfully servicing you - but it doesn't sound like that from your post.
Maybe you can work on encouraging her to be more "aggressive" in the style that you want, but at the same time perhaps you can work on "seeing" the times that she is initiating, in her own way.
Sexual expression is very personal, so please try your best to stay away from characterizing your way as the "right" way and her way as "wrong". My STBXH complained that I was not aggressive and did not initiate enough, but when I made attempts, he would be angry if I didn't do it "right". He would be upset if I said "lets ML tonight" instead of "f***". Your wife is not a wind-up doll who you can program to perfectly act out all your fantasies according to script. If you are always letting her know that you are disappointed in her sexually, and aren't supportive of the attempts that she does make, even if they aren't perfect, I can guarantee she will not become more "wanting" and will be less "willing". That's what happened to me.
But I imagine you love her for the things that make her unique - which should include her sexual personality. Maybe she just needs to learn to express that side of herself a little clearer, and you need to learn to see it clearer. Good luck.
