This has been going on for about 1 week. It started very suddenly. Kitty went from in/out all.day.and.night, waking us multiple times--to now. She has found a spot on the grass near our driveway. She comes in only to eat and immediately goes back to the exact same spot. She has worn the grass away.
She is responsive to petting and will meow in greeting when I come home. She does not seem weak or in pain. She is eating fine and not excessively. I don't notice excessive thirst. Is this lethargy? Someone asked if she's a hunter and she is, but she doesn't seem intensely focused on potential prey out there. She refuses to stay in the house. This seems to have happened literally overnight, but she does not seem distressed. She is at least 16 years old and has never been sick a day in her life. Any ideas? Thanks.