F/u question-can you awaken having anxiety attacks or feel calm & relaxed but still be having an anxiety attack which causes hyperventilating sensations?

Yes and No. Yes, you can certainly be awakened by anxiety. However, if you are truly relaxed, by definition, you are not experiencing anxiety. If your question is, can hyperventilation be your only symptom of anxiety, the answer is yes.
More unlikely. This sounds like a panic attack which is in contrast to a state of calm. In fact, panic attacks most often involve a sensation of intense fear that triggers severe physical reactions. Causes are multiple and can include genetics, stress, mood instability, and neurological changes in brain function. For more answers i would start with a complete physical exam followed by mental health evaluation.