Cats have an instinctive need to feel safe and secure at home. So, it makes sense that if your cat doesn't feel comfortable in their favorite napping spot, they'll look for somewhere else to snooze. This is particularly true if they've had any negative experiences at a specific sleeping spot. For instance, if their owners wake them up at night often or they hear loud noises from the house that disturb their slumber, it will be imprinted in their memory as a place to avoid.
Cats also like to change up their sleeping spots in order to mark their territory. This is especially true for cats who live with multiple other felines, as it lets them distinguish their space from other's. They might even rub against their paws on the carpet, pillow or wall in order to leave a scent that marks their territory for any predators.
Another reason why do cats change where they sleep is that it's simply a matter of survival. If cats become too predictable, they can be easily found by predators. This is why wild cats scratch at their bedding to expose the cool soil underneath and avoid the warm air above.
Finally, a big reason why cats move around their sleeping places is that they're simply looking for warmth. They'll find a spot that feels cozy enough to sleep in. This might include the top of their owner's bed, on a sofa or near a radiator.