My dad is 56 years old, he has been on and off many medications. As of right now he is not taking any. My dad sleeps all the time, and can barely stay focussed when awake. He twitches in his sleep and severely snores all the time. He is even getting his days of the week mixed up as well as hours of the day.
The age 56 is way too young to be doing all that sleeping. Why isn't he employed? One can get very groggy by over-sleeping and that makes it hard to focus.
As Pam said above, your Dad needs a complete physical.