I usually sleep rather well, not always but at about 2.00pm each day, i feel lethargic and feel that I need to lie down. I work out at a gym three times per week, eat well and to the best of my knowledge, I am in good health. I never sleep when i lie down in the afternoon, so i don't know whether it's a physical thing or what. I find it frustrating when I feel this way for no obvious reason. I am 63 years of age.