Tremor

Question
My 13 yr old cocker spaniel Sage has been restless for a couple of nights constantly getting up and down .I noticed that when she is lying on her side asleep one of her back legs has a small tremor in it. She doesn't appear to be in any pain,has a healthy appetite,and doesn't appear to have any issues walking or going to the bathroom. It appears to be more of an aggravation to her than anything. I noticed this once before a few months ago and it went away after a couple of days. Is this a normal progression for a dog of her breed and age? She also only recently has started to have a dry hacking cough which her vet has identified as allergies.Could these two things be related? The vet doesn't seem to be concerned...

Answer
How exactly did your vet diagnose allergies?  What was suggested? (Antihistimines?)
When was her last complete check-up (bloodwork, etc.)?

I'd be quite concerned about the cough.  Did your vet do a complete physical (listen to her heart, lungs, etc)