She seems fine this evening -- eating, playing, chewing, etc. So I guess that's all that it was. I'm glad. She had me worried when she was shivering. She usually is quite calm when I leave in the morning (after her pee and her walk and some play time in the yard, I suspect she goes to sleep right after I leave and only wakes up again when my mom comes by late morning), so when she was shivering when I was leaving this morning, I was concerned.