Thanks for the replies!
I lubed the chain up and now it seems to be a whole lot better. I still notice it, very very slightly, under a ton of pedal pressure, but it's completely tolerable now. I'll have to do better at keeping the chain well lubed. Yesterday is when I was really noticing it, and the chain was definitely dry yesterday when I picked my bike up from storage...!
I'll rest easy knowing that lubing the chain was both suggested as a culprit and seemed to do the trick.
Though now I feel like a bit of a noob...!
Ira B, do you have any follow-up thoughts? Chain, chainrings, or cogs?
Thanks to you both!