I'm 69 Years Old (female) In Relatively Good Health. When

I'm 69 years old (female) in relatively good health. When i take a nap during the day i have a hard time waking up and can sleep for as long as 3 hours even although I slept well the night before. An hour or two after I fell asleep I start to wake up (become aware) and struggle to wake up fully but before I know it I'm asleep again. The cycle can repeat several times before I finally do wake up. I'm not taking any medication.