Asked for Male, 19years old from Hyderabad
there are a few reasons that an adult man may not wake up with a morning erection. Men may not wake with an erection if they're not coming out of rem sleep at that time. Wakefulness is often preceded by lighter stages of sleep when erections do not occur. It's also possible to have rem without having an erection.
A lack of morning erections may also be a sign of erectile dysfunction (ed) or impotence. If a man is experiencing erectile dysfunction at other times, whether or not he has a spontaneous morning erection is a clue his healthcare provider can use in the diagnosis of what is causing the problem.