Anybody else doing this?

I have found lately that in the late afternoon,,around 4 or 5,,I need a short nap!1 I just get really tired! So, since I am retired,,I take one. My cat and dog ar getting used to it now,,and take one with me! A friend of mine that is 13 months out,,said she has had to do that too,,started around her 6th month.She is a lot younger than me, so I know its not the age thing. I feel great,,I just get tired. Just wondering if anyone else has noticed this too. I sleep like a baby at night and wake up earlier than I used to. maybe thats why....