I have erectile dysfunction due to a wreck back in 2015. i can achieve somewhat of an erection with medication. but i have woken up with an erection suitable for sexual intercourse while in the dead if night. what could cause my erectile dysfunction?

It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. It would be prudent to see a doctor, preferably a urologist. Wish you good health!

Normal erection at night is a good sign. You should see a Urologist sub-specializing in ED for proper evaluation and treatment. May be the right ED med in proper doses might correct your problem. Good luck