Shaking is quite a non-specific sign and can be an indication of fear, stress, pain, nausea or metabolic issues such as abnormal salt levels.
If he has no other symptoms which could help us to figure out what is going on, the first place to start is to do a full physical and neurological exam, checking him from nose to tail to look for anything abnormal that may be causing the issue. Something small like a broken tooth or impacted anal gland may be the cause and is not easy for an owner to spot. Similarly, any sore joint or orthopaedic issue would be picked up.
If his exam is unremarkable, normally the next step would be a basic blood and urine test. Diseases such as Addison's disease can result in shaking and other vague symptoms, and these dogs will have abnormal salt levels. Similarly, we want to check for any underlying issues such as a liver issue or kidney function issue, as well as a potential urine infection.
It would be worthwhile taking a video of the shaking events with you so the vet can see them. In some cases, a partial seizure may disguise itself as tremoring, and a vet should be able to tell from a video.
A referral to a neurologist could also be worthwhile, in case of a rare condition. In some cases, imaging of the brain and spinal cord are also advised.
Before assuming it is anxiety related (which is quite possible) we need to rule out other causes.
Issues such as joint pain, Addison's disease or nausea should respond well to medication.
If these disease are all ruled out, it may well prove to be anxiety related, particularly if you notice a particular pattern to the events e.g. triggered by loud noises. In these cases, calming supplements, pheromone collars and plug-ins as well as behavioural modification programmes tend to give the best results. While it can take time to address anxiety related tremors, there is certainly lots that can be done.
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