I deal with a panic disorder and what you're describing sounds super similar to what a garden-variety panic attack is like. Especially the part about your heart rate rising but your oxygen saturation staying pretty much the same (the difference between 94-97 and 97-100 is within the normal variation during physical activity). What's likely happening is that your brain is latching onto some small thing, like laying down on your back and putting more pressure on your diaphragm. Instead of interpreting that small thing as totally normal, your brain interprets it as a "warning sign," because of your stress/anxiety around COVID, and it goes into panic mode. At this point, it's pumping out a lot of chemicals that stimulate what's called a "fight or flight" response; it's your natural response to any perceived threat, real or otherwise. Those chemicals will cause your heart rate to increase and will often cause shortness of breath. Usually these can last 45 minutes-a few hours and will subside. Deep breathing exercises work for some people, but I find that when I focus on my breathing I end up spiraling more, so I focus on grounding exercises and progressive muscle relaxation. I'd recommend trying those out next time you have a bout of that and see if it helps :)!