I had something weird going on for about 1.5 months. I thought COVID was a possibility at one point but really doubted it. Didn't bother trying to get tested because I assumed I wouldn't be allowed as I wasn't obviously sick enough. The main thing that bothered me was I just couldn't figure out what the hell it was (everything medical had been ruled out). But after reading these posts, it makes me wonder.
The main symptoms were a major increase in heart rate and feeling out of shape on runs. For reference, before this started, runs at 7:45ish pace would start out at 120bpm and then settle in the 130-140 range for the rest of the run. At the worst of this, at the same pace, it would start out at 150 and would get to 170-175 by the end of the run.
Started in early march. One day the heart rate was suddenly 10 beats higher than usual on a run. I also felt "out of shape" with my breathing sounding/feeling more noticeable, but effort on easy runs still felt easy. Shrugged it off to something random that would go away shortly. A few days later is when RHR started increasing. Started at 36 and was up to 48 within a week later (saw it increasing every morning). Heart rate continued getting higher on runs for the next few weeks and the out of shape feeling was becoming more apparent. Soon, easy runs began feeling bad and more like a tempo run. 7:30's felt more like 6:30's, was really discouraging. Also, I could feel my heart pounding away throughout the day and I just felt unwell overall. Didn't really feel like it was a virus, felt more like a medical condition, which is why I got checked for that stuff. I would get winded from doing strides or any sort of short, fast, movement. There were random days where resting and running heart rate were pretty much normal, which made me think I was getting better, but it would go right back to what it was within a day or two.
Then there was a brief period in early April where I couldn't sleep at all. It seemed like it was because I just couldn't get my heart rate to calm down. The out of shape feeling on runs was at still at it's worst during this time, too. Finally, about a week ago, things seem to be going better. Decided to finally try a workout and ended up doing reasonably well. The out of shape feeling on runs is gone. Heart rate is now 140s-150s on easy runs, so not completely what it used to be, but much better than a month ago. RHR has also calmed down to 42/43.
Other things I noticed during all of this is the weird feeling in the chest that some on here have mentioned. It felt like a mass was wedged in there. Whenever I held my breath I would feel it deep in my throat and my right chest would have a weird throbbing sensation. I couldn't hold my breath as long as I usually could either. I had feverish feelings that would come and go, and throat was a little sore/scratchy at times.