Shaking w/ fear

Mattingly has always been a skiddish dog. He's not trustworthy of strangers and he picks and chooses when he lets even me love on him. But he's recently started shaking like a leaf when he's put in his kennel for the day. He's been crated while I'm not home for his entire 7 years of life and never done this before. Any ideas what could be causing this shaking?

BTW: Mattingly is epileptic and is on medication. I know they're not seizures.

Thanks Friends! Holly, Matt's mommy