Moto G5 plus, though issue has been known to occur in many G5 and G6 models.
“Settings; Storage” does not work, just shows a loading screen forever.
I searched for answers for days, and finally found one better than a factory reset.
I went into “settings; apps” and starting clearing the cache in my apps, one at a time. When I got to “Chrome,” it had almost a gig of cache and was hard to clear. I pressed “clear cache,” waited, hit “clear cache” again, backed out of the app details, went back in: cache was smaller! I cleared it 10-12x, and it took like ten minutes to get to zero, but once that was clean, “Storage” worked again.
I suppose it could be any cache-hog app, Chrome, Facebook, Amazon, etc, but the cache was definitely hanging it up.