Inability to have an erection during sex, but erection on its own during sleep may be related to psycho-psychological, social and family factors. 1. Spiritual psychology: If men have had bad sexual experiences, or if they are anxious, depressed, withdrawn, or lack self-confidence, and are too tense and fearful during sex, they are prone to not being able to have an erection, because they are in a relaxed state when they sleep, so they can have an erection on their own. 2. Social factors: If the recent life is too much pressure, or interpersonal relationships are more complex, to a certain extent, will also affect the penile erection, to sleep when the erection of the situation. 3. Family factors: If the relationship between husband and wife is not harmonious, there is a gap between each other, feelings of indifference, men will appear in the sexual life will not be able to get an erection, but the phenomenon of sleep can be erected on their own. It is recommended that men who can’t get an erection during sex, but can get an erection on their own in their sleep, go to the hospital to get a clear understanding of the cause, and then actively treat the problem.