Lucy has days like this ... and we seem to have figured it out. You say that you've walked her, played with her, etc - but when Lucy does this, it seems to translate as: "yeah ... but not ENOUGH!"
If it gets too much, I usually just lie on the sofa with one of her favourite toys and play tuggy with her ... she usually plays for about another 10 minutes or so and then gives in to snuggle up and have kisses before dropping off to sleep.
When we got a yorkie, people kept saying "oh, well she won't need much exercise". Um ... you've just got to be kidding! She's like a baby whirlwind, and enough never seems to be enough.