@rrradar
Definitely, something is wrong, and he's lucky to have a caring friend in his life.
Unfortunately, we cannot diagnose on this forum as most of us are not physicians. That being said, your friend should start with a visit to his family physician for a complete check up with labs. There are several conditions that can cause the symptoms you describe including Sleep Apnea which results in excessive daytime fatigue and the ability to fall asleep at will. Other problems could include abnormal nocturnal biorhythms. Even some neurological conditions could be the culprit.
Please get your friend to a doctor as soon as possible, as a secondary concern could be that he may aspirate (suck food or liquid down his throat)on food left in his mouth while falling asleep which will cause Pneumonia.