Saying do you want to have sex is one of my biggest pet peeves. My husband does this and it drives me crazy!!! Lol from my experience sex that occurs after being asked is usually not as good and passionate. But sex that occurs organically, without talking about it is always amazing. The unexpected, unplanned sex is usually the best.
while I strongly agree that his wife or most any women feel this way about being asked for sex, one has to step back and acknowledge in situations when intimacy is becoming complicated there has to be a system in place that allows a couple to designate a safe and nurturing times to work on intimacy. He is going to have to find "some way" to communicate with her.
there are some indirect ways you can ask your wife to have sex AND work on trying to make things more natural for her. You have mentioned that she does claim to enjoy sex, so you should ask her that if she has noticed an ideal time of day that she is the most receptive towards enjoying sex? This can give her an opportunity to tell you for example that she is just not a morning person and that no matter how hard you try in the mornings that nothing will ever happen. She may also say that by the end of the day that she may often be too fatigued most of the time and have little or no patience left to try and get herself into a playful mood. As a result she may find that lunchtime is her ideal time, because she is energized and in the mood to enjoy a break.
Once you establish that, you can learn better how to plan a romantic moment with her that actually stands a fair chance of being enjoyable.
You can also talk to your wife during a non-intimate moment about asking her what things if any that she finds annoying during sex. She may tell you that she gets really annoyed when you ask too many questions DURING sex. And if you are hesitating to try something new or different, you can run those ideas by her outside the bedroom to see if she has any objections to any of them. You may find that your wife is completely OK with trying anal sex, but that it would only be OK under very specific conditions like while playing around in the shower so that any hygiene issues are easily mitigated. This way the next time you are being playful in the shower, you don't have to ask if you want to go exploring a little. I am using this unusual example just to demonstrate how you can ask more questions outside the bedroom, so that when an intimate moment happens that you have very clear knowledge about what is OK and what is not so that you can be more playful without asking questions.
Regarding oral, perhaps that is something she feels comfortable exploring immediately following a shower so that she is not self conscious about her hygiene and can relax. Meanwhile if you find yourself getting intimate immediately after she has been working in the yard, you know not to even go there. But you have to ask her these things, and NOT during sex!!!!!!!!!! Ask during pizza and watching sports together on TV.