Welcome to the group . . . so glad you decided to come here and share your experience . . .
I am not a med professional so my answer is from personal experience . . . although I have not had exactly the same symptom as you have had, I had had episodes of anxiety and panic that left me trembling . . . it is an extremely unsettling experience . . . . for me, I am fortunate because, for now at least, I seem to be in a more stable period but I do hate what I call the "shakes" . . . I think, for me, this comes for the fight or flight and rushes of adrenaline when I have an episode . . . because you have had issues with anxiety from your 20s, I suspect that anxiety may be a root cause although you really need to see a medical practitioner for a comprehensive check up . . . my only remedy (and it was not a quick one and not one that works 100% of the time) was to change my lifestyle and apply management techniques to deal with my anxiety . . . if your symptoms are entrenched in your GAD, then you also could benefit from similar changes and/or medication and/or counseling, etc.
Of greater importance, however, is for you to know that you are not alone . . . we may not be able to diagnose your issues because we aren't medical people, but we are a nice bunch of people here . . . I've been coming here for just over a year and it is a very welcoming forum that has participants who are willing to share their experiences, offer their suggestions, and support each other in whatever way they can to help someone inch closer to stability or recovery . . . . so, never think that you are alone in dealing with your GAD and thank you for adding your voice to all of ours . . . take care, kc