Why do penis erect in the morning or when we wake up?

I'm very curious about this. Why do my penis erect when i get up from bed? Serious answers please. And is there any way that can be done so that it doesn't erect everytime i wake up? I'm asking this because my mom actually saw my dick erecting when she was waking me up for school and i forgot to lock my... show more I'm very curious about this. Why do my penis erect when i get up from bed? Serious answers please. And is there any way that can be done so that it doesn't erect everytime i wake up? I'm asking this because my mom actually saw my dick erecting when she was waking me up for school and i forgot to lock my door. And seriously its really embarrassing. Hope you guys could give me good answers. :)
8 answers