It is extremely common for women who are very independent in most parts of their lives to want to be submissive in their intimate lives. Sexual arousal is a very primitive part of us, and the dom/sub vibe in the bedroom seems to tap into that. It's normal -- don't worry about it.
Have you clearly communicated your preferences to him? Don't expect him to be a mind reader. And don't think that he'll be offended by your giving him information about yourself in a non-demanding way. Men are often grateful for that. For example, you could say, "I love it when you initiate sex. It's such a turn-on for me. And if you do it and I'm not in the mood, I promise that I'll let you down easy / give you a rain check for another time / [whatever]."
It could be that he is a natural sexual dominant and that he would initiate freely and often if he thought it wouldn't offend you. Alternatively, it could be that he is not so dominant, or that he has mixed feelings about being dominant. If that's the case, there are things you can do to help bring out that side of him. But there's no point worrying about that until you first let him know exactly how you feel.
