If your cat had previously not exhibited this behavior, it sounds like s/he either doesn't feel well, or something has frightened him/her and is seeking extra security.
Sometimes, cats can become stressed/anxious by any changes in the environment or routine. If you've recently had house guests, made any changes around the house, like moving furniture around, getting new furniture, appliances, preparing the house for the holidays, adding a Christmas tree, etc., there are scents and sounds would can be causing her anxiety.
If your cat is eating, drinking and eliminating normally, plus, is active/alert during the day, that's good, but a vet evaluation, ASAP, would be a good idea. Once any medical reasons are definitely ruled out, you can treat this problem as behavioral. Try a cat appeasing pheromone called Feliway/Comfort Zone for Cats, which comes in both a spray and plug-in diffuser, available at major pet supply stores like Petsmart, and also online. The diffuser resembles a plug-in air freshener, but has no scent to humans. Feliway helps to relax stressed cats and is useful in a multitude of situations. For more information, please see: www.catfaeries.com/feliway.html
I hope all will be well with your kitty!