thank you for your reply. You have given me a new avenue to try with thyroid issue - I don't think my vet tried this. would thyroid issues "come and go"? the symptoms show for about 3 weeks and then he is ok-ish for about a week before licking, bum shuffling, leg trembles etc start again. You mention that a metal collar would normally create rash or loss of fur if he is allergic. the collar is a very loose choke-chain and would only come into contact when he laid on it.
he has these symptoms regularly throughout the year - this makes me think that is not pollen/grass related with winter season being dormant.
When he has what my vet calls an "episode", he has violent scratching at the left side of his mouth; just prior to the episode, excitement (or stress) seems to trigger something that seems to cause pain at this place in his mouth. This is the only place he scratches. I usually grab hold of him and stop the scratching when I can - it takes a few moments for him to respond to my care. I just wish I could have my healthy happy furry pal back as he was - loved walks - now it is an effort for him to keep up with my slow pace...!