I,ve got a 11 month old golden boy and he trembled terribly when he was going to sleep and when he was put into the car.Studying him every time he did it,i worked out it was because he was cold(it was in the winter)He has all ways been a fussy eater,and its a constant battle to get the weight on him,so he isnt carrying much insulation in that respect.It really worried me at the time before i realised why he was doing it,as all my other cockers are on permanent diets because they will stuff both ends given the chance.
Now that he has a good coat covering(he isnt hairy,has a non strip coat)and its got warmer he hasnt done it for ages.I am going to buy him a coat though,for next winter as i think he will feel the cold more.