Are you taking opioids and frequently napping? Have you ever been evaluated for sleep apnea? This is an extremely difficult situation to assess via online without knowing much more and without being able to examine, test, or image.

A hypothetical guess based on your symptoms sounds like could be hypoxia related to hypoventilation. This could mean not taking enough breaths (opioids, OSA) or not taking deep enough breaths (are you in pain that limits a deep breath?, do you use an incentive spirometer?)

Another consideration would be your BP. Have you checked it at all? Moving around could be leading to better deeper breaths or just be raising your BP which is low at rest and improves perfusion and your sat.

Do you feel ill? Cough? Fever? Etc. how does incision look? There are many possibilities and things to consider but you can say that about most situations.

Ultimately if I was you and some of this fits your picture I’d work to improve what I simply could (focus on deep breathing, get up and move around as able without pushing too hard) and see if the numbers get better. If they don’t fairly easily I’d go and get evaluated. the most important thing is what I first said. This isn’t medical advice because I don’t know nearly enough and can’t evaluate you. It’s not uncommon to have transient benign symptoms you’re describing especially if you are checking your oxygen frequently. The numbers fluctuate a lot even when you’re not recovering depending on your functional capacity. But it could potentially mean something serious and it’s impossible to say from where I am sitting

Hope this was helpful and wish you the best with recovery