This set of posts comes from Pastor Mark Driscoll and his wife Grace. The sermon series The Peasant Princess brought up dozens of questions that they felt they should respond to. The result is this blog series: Christian Sex: Frank Answers to Honest Questions.
Answer: Do not deprive one another, except perhaps by agreement for a limited time, that you may devote yourselves to prayer; but then come together again, so that Satan may not tempt you because of your lack of self-control. (1 Cor. 7:5)
Christian marriage is about loving, mutual service both in and out of the bedroom. There will be times when one spouse is in the mood and the other is not. Those are occasions for the spouse who is not in the mood to serve the other in love, knowing that there will be times when the scenario is reversed and they too will be served. God often blesses this kind of covenantal loving obedience and changes the spouse's desires so that they are both in the mood once they begin their intimacy. If not being in the mood is habitual, there is usually something that needs to be worked on outside of the bedroom (communication, past abuse, hurt, argument, etc.). At times there might need to be an emotional connection before the physical connection can be enjoyed or desired.