I get this often and it scares me. It happened just now, I've been fine all day now I've been sitting on the sofa watching tv and all of a sudden, out of the blue, I felt weak (internal weakness and weak feeling in the arms), heart racing, breathless feeling, hot and panicky. I walked into the kitchen to get a drink and felt awful. It's subsided but I still feel on edge and a bit weak and now feel really, really tired. I hate this, it really scares me.