I get this feeling too except it's just in my upper torso, it feels like my lungs and and heart and all my muscles are trembling. It only calms down for me after I take my atenolol, even though it's blood pressure medicine I don't take it for that. When I go to sleep I'm fine but I wake up every couple hours it starts and It's hard to go back to sleep. My doctor told me the trembling is because of adrenaline caused by anxiety. Although I never knew anxiety caused all that much adrenaline problems but I'm new to learning about all this stuff.