My only Yorkie that shakes is Cash, the first time he did I got so scared I took him to the vet
and the vet said it's nothing he's just excited or scared, lots of little ones do it
Now every time he knows he's going to the vet his little lip just trembles, it really is cute
The only other time I see him tremble is when he's going to get snack
It's like he's so happy he can't help but tremble