Full body tremors and shaking

Sorry I’ve been posting so much but I have one last question. A few weeks ago I started to tremble and shake all over uncontrollably. Like muscle spasms almost. It came in waves. Trying to relax wouldn’t stop it. I got so scared we went to the ER, and they thought it might be me withdrawing from my anx/depres medication because I forgot to take it for a few days. So okay, I go home and take it, an hour later it subsides. Then the other night it happened again and I had been taking my medication properly. It comes with that horrible anxiety only chs produces and a heart rate increase to like 170-200bmp. It went away eventually but has anyone experienced this?? Or is it something else entirely. Such a horrible sensation.