Sudden breathing issues and chest tightness - POTS?

Was this right when you put the pulse ox on? You have to give it a minute or two to get a clear o2 reading. Especially if your HR is high, it makes it a little longer to read the o2 correctly.

Im not sure if it's POTS seeing as how symptoms differ between patients, but it is something I would definitely get checked by a medical professional. See if your physician refers you to a cardiologist.

It sounds the same as i had experienced. I almost never smdo stairs or elevators anymore. Any physical stuff, i keep for like between noon and 4. Seems related to aldosterone levels being high in the morning. Then getting tired early in the evening.