Hi Andy, MeSci and Out2lunch,
I am still not sure what is going on but have noticed that they seem to be related to potassium, sodium and perhaps metafolin and b12.
A month ago or thereabouts, I seriously increased my sodium and potassium intake, taking enough to bring my urine to neutral in the evening, but not enough to make it neutral in the morning.
Most of this was because I had a full body viral rash and having read that potassium was important for the immune system on the enterovirus foundation's site
http://enterovirusfoundation.org/immuneboosters.shtml: reading the info at
http://lpi.oregonstate.edu/mic/minerals/potassium.
I found that 3-4 tsp potassium chloride was working well for me with about 2-3 tsp salt. Note that my immune system was probably pretty active: it was a really nasty rash, and my usual dietary potassium is high 6-11g.
Last week my doctor asked me to reduce the amout of potassium I was taking, because some pathology I had done about 30-60 minutes after taking a tsp of potasssium chloride showed me at 5.2 and 5.4 is apparently a bad place to visit.
so I decided to step back on potassium, salt and the metafolin that was probably also accelerating my need for potassium.
I had palpitations, and vibrations strong enough to wake me over the next couple of days. I tried some experiments trying to see if it was the potassium or the salt that was most effective at stilling the vibrations, but it seemed that the vibrations only stopped when I added the metafolin.
I susupect that the potassium is most important for palpitations; salt for POTS; magnesium for muscular spasms and perhaps the metafolin for the vibrations.
I have noticed that B12, which seems to relax me when I need it, might be important for vibrations too.
This B12 thing might fit in with Andy's observation about it striking when the mucles are tired. For me it tends to be afternoon/ evening when I am resting/ need to rest and early morning say 5am - 9am.
But it is hard to know, the ideal experimental conditions occure at moments (or for hours or days) when I am least able to consider these things carefully.