I have found that the ONLY variable that has been constant before the late afternoon or post supper trembling attacks is that I have always eaten several squares of a 90% cocoa bar after lunch —- tastes great to me and supposedly has health benefits. Other food and activities can happen at other times. The trembling is accompanied by high blood pressure, a link found by a nurse friend.
This seems a strange possible cause, but I found a study by Consumers Reports that found unsafe levels of heavy metals in dark chocolate. I cut it out for 4 days now and have had no HBP, but it is too soon to judge anything.