I've had anxiety for a long time and i know the feeling well. However for the last few days I've been getting a sort of alarming feeling randomly throughout the day, it's the same kind of feeling when you don't feel your phone in your pocket, like suddenly your heart beats super fast for a few seconds. When it's been happening, I've just been going about my day and whatever I've been doing is definitely nothing to panic me. Has anyone else had this before?