Our cats will once in a very great while settle in for a very long sleep or rest n the same spot. It usually includes a lack of appetite too. We assume it is the equivalent of our kitties getting colds, because when they get up they are lethargic for another half day. But, then they recover and are fine.
My cats never stay still for that long. The only time they stay put is when I am laying down. They are always by me unless they are eating, in the litter box, I'm not here or go outside exploring.