Try pantethine and pantothenic acid combo. What worked for me may not be the answer for you, though. 300mgs 4times a day with 2,000-3,000 mgs of ascorbic acid if you can tolerate it. This helped me with those symptoms. After dealing with this over a decade I can see a lot of it for me is needing to address low mineral levels and high copper as well as other toxic metals. Nutritional balancing is making quite a difference for me. I think I'm about 7 months in total with the supplements. I can now tolerate Iodine because of this program which is also making a very big difference. Progesterone cream is also helping, but I'm a female. I've got about 9 years posting on this forum if you want to look back through my history on here, though I rarely post anymore.

It is worth taking your blood pressure and body temperature (under tongue) when you have these shivering episodes.

I have had similar symptoms, and can relate to the tremors in the body - sometimes i wouldn't be able to stand, during these episodes i would have a low BP of around 70/50.

Do you ever experience intense sweating, nausea, then vomiting before the shivers, tremors and stomach feelings?
That would be very similar to an adrenal crisis and normally collapse follows yet you say your cortisol tests show low-normal and high night.
Maybe you have highs and dips in your cortisol levels which the 4X test won't necessarily pick up, and perhaps these episodes are adrenal related.

After an adrenal crisis of back pain, intense heat/ vomiting /collapse i would shiver violently, my skin would turn blueish, body temperature drops to 34.5C, low BP.

But sometimes i would have just the shivers, tremors, weakness, nausea - which was adrenal related for me.

So to see if it adrenal related take your BP and body temp during these episodes.
That can reveal a lot.

They say neurotranmitters work on a 'see-saw' - so if one is high, the related other is low - like dopamine and serotonin.
Theoretically, if you were to take 5-HTP, that would boost serotonin and lower dopamine - have you tried that?

I'm not personally sure if urine neurotransmitter tests are reliable due to results being measured from waste.
For example, If the body has a hard time breaking down adrenaline to be filtered by kidneys into urine, There will be a low reading. That doesn't necessarily mean the body isn't producing enough adrenaline - it *could be* the body cannot break down and excrete adrenalin well.

Many enzymes have to work well in order for neurotransmitters to be synthesised and excreted.
If we just measure wast products to gauge production levels - there is a wide margin of error in that approach and the assumption is that the body is making and excreting these products normally - which in a ill person, is unlikely to be the case.

This could be the reason why your methods of trying to balance based on your test results have not given you the results you'd hoped.

From my research so far i haven't come across an *accurate* testing modality for neurotransmitters - admittedly i would like to research this more but i am yet to see a study where blood and urine neuro levels matched spinal fluid levels.

Neuro-imbalances are generally more easily diagnosed through symptoms coupled with test results of serum/urine by an experienced neuro practitioner - orthomolecular practitioners tend to have a better idea of what presents with neurotransmitter imbalances.

I'm not sure it's possible to have high cortisol and low adrenaline as cortisol production is generally triggered by adrenaline resease, certainly in the case of 'life' stress, also in the case of physical injury too.

Do you startle easily? Have a fast heartbeat? Sweat more than usual? Feel jittery? Eat anything and not get fat? Nervous energy? Fast thoughts?
OCD tendencies?

Caffeine triggers an adrenaline release - what effect does caffeine have on you? Do you feel revived by it? Over-stimulated by it? Sluggish? Brain fog?

If we know what foods give us symptoms it can help us identify what it is in those foods which potentially is causing body chemical reactions that's creating imbalance.
Like histamine - i was gobbling bananas, not realising they were big histamine triggers - while having severe allergic responses to heat and fly bites. Big whelts would appear and not go for days.
So i cut down on all histamine producing foods and found these reactions lessened.
It is not a cure, afterall why my body produces too much histamine still has to be known, but it helps to at least discover levels are high and avoiding foods making it higher reduces symptoms.

Make a note of all foods/supplements which create a reaction, write down the symptoms associated with them - and while you are on your healing journey bits of the puzzle will start to make sense for you when you learn more about your personal body chemistry and imbalances and what it is in foods which make those imbalances worse or better. THEN you'll get to truly know what your true levels are, whether high or low.