Why is my dog sleeping almost the entire day?

by Mayela fernandez
(Texas)

My dog just turned 1 year old in september so she is relativly young, i play with her for about 45 minutes every day and one we stop playing, she goes to asleep. When she hears a noise shes on alert and ready to charge. A couple of minutes later she goes back to sleep or scratches on the door so that she can use the restroom outside.she eats well and drinks alot of water. Shes really playful when she isnt asleep. Should i be worried if she is sleeping almost the entire day but when she isnt asleep shes playing?