Is there something wrong with my young lethargic cat?

My one year old cat is usually very playful and loves feathers and q-tips. She is normally a bit grawly and will try to push away. However recently she's been hiding underneath my bed, something she's never done, and when she grawls, she still snuggles up against me instead of trying to push away. There are no new animals in the house, and she is eating and drinking normally. She has all of her shots, spayed and has been vaccinated for feline leukemia. She's also an indoor cat only. Should I be worried??