I found your issue a bit puzzling as it fits a pattern in which the coil built could be just coincidental. As suggested above, a reaction to the built up gunk on the coil sounds plausible. These symptoms are also very typical during smoking cessation and can last quite awhile... I haven't found a straight response to why this is happening. Can it happens when the vaping settings are changed? I feel sometime the same way after a pushy endurance run but these symptoms disappear quickly after the phlegm stuck in my lungs clears out and it's becoming less frequent the further I'm navigating away from smoking.
The gunk thing could be it, im not really ruling anything out at this point, some things just seem less likely then others. The gunk thing mainly because its day one or two of using the new build, just doesnt seem it would be gunked up that fast, but then again with the excess juice issue.
I quit smoking a long time ago, and had some issues at first, but they cleared up a week or two into vaping. The settings and stuff i am not changing, usually just toss it on the 7watt ipv and vape like usual, just occasionally my chest doesnt like it.
You are pretty close with the running thing, that is sort of how it feels, if my out of shape ... runs and my chest starts hurting/burning, i would compare it more towards a chest cold, congestion, bronchitis type burn though, and it clears up fast once i change the build, the thing thats getting me is if all i am doing is rebuilding, not changing juices or settings, then why does it go away?