Your father may simply be showing signs of normal aging. My father keeps dozing off at odd times, and he seems pretty forgetful. Your father should talk to a doctor if either his sleepiness or his forgetfulness is interfering with the normal tasks of daily life. Your father may simply be showing signs of normal aging. Starting around age 65, many people find that their sleep becomes lighter and more fragmented.
Many elderly people have trouble sleeping at night.
They wake up in the morning feeling tired and sometimes doze during the day. So nodding off occasionally after lunch or dinner is probably nothing to worry about. But if your father is getting drowsy in the middle of conversations, while driving, or while working outdoors, he should see a doctor. He could be suffering from a sleep disorder such as nocturnal myoclonus, which produces abnormal leg movements at night, or from sleep apnea, a breathing disorder, both of which seem to occur more frequently in the elderly. Both conditions can cause disrupted sleep and daytime drowsiness.