Normally, blood circulates into your penis through the arteries, and out again through the veins. When you are sexually stimulated, tiny muscle rings around the veins contract, which prevents the blood being pumped in by the arteries from leaving the penis. The penis is therefore pumped up to an erect position by the blood entering through the arteries. An early morning erection is a very common phenomenon, and is caused by mildly erotic dreams, and stimulation of the nervous system controlling the blood valves in the penis, while asleep. There is nothing abnormal about these erections at all, and they normally subside rapidly on awaking. There is nothing wrong with sex in the morning, the afternoon, or at any time provided it is desired by both partners. When it is desired by only one partner (male or female) and forced upon the other, sex becomes rape. If there is a problem between you and your wife over sex in the morning, and you have difficulty in obtaining an erection at other times, a calm rational discussion of the problem, at some other time of day, is essential. If you cannot resolve this conflict, marriage guidance by your doctor or a counselor becomes imperative.