We have a very sweet bantam d'uccle who when held kind of vibrates on and off when you are holding her. Very rhythmic. She is not afraid of us and will come to us to be picked up. I never thought much about it but today she seems a little lethargic, like maybe something is wrong, and her vibrations/shaking are a lot stronger when we hold her. It is visible in her feet. She shouldn't be cold either - 70 degrees outside. (We're in FL) Any ideas? Should I be concerned?