There's no reason you can't initiate sex rather than waiting for him to get things started (many guys find it an incredible turn-on to have the woman initiate sex every now and then).

If that doesn't work, don't worry - anyone can have an off week for any of several reasons. Give it a little longer and try not to pressure him about it. If this continues for another week or two, or you notice signs in other parts of his life that may suggest he's ill or under crushing stress (two potential causes for lack of desire), talk to him and see what you can do to help. If he's started taking any prescription medications recently, that may be the culprit (the drug companies don't like to admit it, but many drugs have the potential side effect of killing libido - some anti-depressants and heart medications are absolutely notorious for it).