This happened to me for a long time now, i could be drinking water all day and always make sure i eat. I have also had bloody sugar tests and all that and it’s all come back fine. Anything physical i feel like it’s a trigger for anxiety/stress, i remember cleaning my bedroom and after i felt that way. Yesterday i finished work and felt so lightheaded and shaky, it eventually faded just before bedtime. I believe part of my legs feeling shaky is probably because of my legs muscle being fatigued from anxiety/stress i suffer in general.