Dog head tremors

I don't know where to begin with this so I'll start with what's happened leading up to this point.
About a week ago Mulligan (Jack Russel mix dog, 1 year, 1 month old) got sick, throwing up occasionally, lost his appetite, had some diarrhea, the first day he only ate rice and broth. The second day he was still having diarrhea but no more vomiting, this is also probably the most stressful day he's had in a bit because we had family arrive and a bit after they left a friend came over ( my dog is terrified of people by the way, he barks, shakes, growls and avoids people. If they ignore him long enough then he'll start checking him out) on this day he also ate some dog food and drank some water today. Day 3 the family came back by for a few hours and once again he barked, etc. At the end of the day his head started shaking ( video linked below) we have him CBD, turmeric and charcoal. Day 4, which is today, this morning he started shaking his head again, not as violently as last night but he was still doing it, gave him more CBD and he's been fine since then. I plan on keeping him downstairs while family is here this evening so he gets a break. Tomorrow after I drop my boyfriend off at work I plan to stop by the vet and see what they say about it.
Here's the link to the video: https://youtu.be/Mb8wszZWa1E

I'm looking for any and all advice, has this happened to you? What was the cause/result? I already plan to take him to the vet so I don't need 5 million just take him to the vet responses.

My guess would be it's just overall body shakes from being nervous or stressed but the muscles were only twitching enough to cause visible movement in the neck and shoulders. Possibly because they have to keep some tension to raise the head. Uneven muscle contractions will be more obvious when they are in use. A vet would probably suggest something along the line of the benzo for humans or a sedating antihistamine like benadryl and chlorpheniramine. The second is just a lesser known otc 1st generation antihistamine that can be used in people and animals. It's stronger than benadryl and I take it before bed as well as having a dog that vomits benadryl so she has to take an alternative. All 1st gens also have psychiatric effects and will even alter neurotransmitter use or levels in the brain. Dopamine is impacted by benadryl and chlorpheniramine is a serotonin reuptake inhibitor(sri). SRIs are the major effect most antidepressants and anxiolytics besides benzos, which alter gaba, rely on. Also why so few 1st gens are used today as antihistamines and only 3 remain otc with one nearly exclusively sold as a sleep aid instead.

Phosphatidylserine(PS) might be useful. It is proven to lower cortisol from stress or a variety of disorders. There is a prescription version combined with omega fatty acids for the treatment of adhd. I take Seriphos brand every night as well after a high cortisol test. Original studies extracted it from cow brains but with mad cow disease they now sell it as phosphylated serine derived from plant lecithin sources and that results in it being difficult to sort the quality products from the ones that the chemistry isn't quite right to function as it's supposed to. That's why I just stick to the more expensive Seriphos formula instead of testing the cheaper formulas by companies like NOW that I would normally buy to get good quality at good cost. In a quick search shows it is mentioned a few places for dogs. This site is selling a product by a high quality human supplement company with phosphatidylserine 70mg per 25lbs https://www.onlynaturalpet.com/products ... 10004.aspx and I glanced over this abstract of using PS in dogs or cats https://www.journalvetbehavior.com/arti ... 58-7878(07)00219-5/abstract. If I had time I could probably find more proven information on use and dosage but my husband's family is doing mother's day stuff.

The second link sent me to an error page. The first link works, I'll look into it a bit and see if I can find any info. Everyone is celebrating mothers day and I'm over here stressed about a dog and my tore belt on the car. *sigh* it's been a long, rough day

For some reason it didn't automatically turn the whole url into a link. https://www.journalvetbehavior.com/article/S1558-7878(07)00219-5/abstract PS has been tested more for it's other effects and long term benefits to brain function rather than immediate relief of any symptoms and you mostly have to look at studies in humans to find it's mental benefits. The effects of cortisol and lowering it in humans is well documented for stopping cycles of anxiety and it's available otc with massive doses tested alongside other medications without any major or lasting physical side effects in human or animal. Senilife is one product for dogs at 25mg of PS in the formula for 50lbs and under https://www.amazon.com/CEVA-Animal-Heal ... B01MUBAR5X It hasn't really gained popularity for even people to try yet so there are probably limited dog specific products and especially behavior/psychiatric specific.

I'm so sorry I completely forgot to reply. So I took Mulligan to the vet and she said she thinks he got trash gut from either eating trash or rotten eggs. She said the head tremors were probably idiopathic. He's since been fixed and had a few episodes of tremors when he's had stressful days.