What Causes Fluttering Sensations With Shakiness And Headache?

I have been experiencing frequent fluttering sensations over the past 3 days along with shakiness and headaches. The fluttering feels the same as going over railroad tracks, riding roller coasters, and the feeling of nervousness, only it happens even when I am at rest on the sofa. I ve tried researching this and all I can find is fight or flight and anxiety. I do not feel anxious or nervous, and I am 100% not pregnant.