I also have the palpatations/heart rate and shortness of breath issues as well. Multiple tests were negative until I had a 21 day monitor. My heart would start racing for periods while at rest, as well as when first standing up and moving. The cardiologist started me on a 'Beta-Blocker' which has made a HUGE different with not only the heart rate, but the shortness of breath as well. Prior to the monitor all my Drs told me the palpitations were related to deconditioning, not being as active as I was before COVID but the continuous monitor told the real story, in real time, in my real life. There is a difference between POTS (Postural Orthopedic Tachycardia Syndrome), which is a fast heart rate most often seen when standing from a seated or laying position. I have Inappropriate Sinus Tachycardia which is a fast heart rate that is not dependent on position changes. Watch out for lightheadedness/dizziness with position changes, take your time standing up, sit at the side of the bed for a moment before standing, then stand in place a moment before walking-you don't want a fall to happen in addition to your other problems.