This was a recurring problem for a few months, occurring usually shortly after getting up in the morning, but sometimes during the night. The connections that I was able to make were that the hives occurred in areas where there had been pressure over a period of time. Since I generally sleep on my side, the anterior portion of my arms was a common spot since I would move from one side to another, and at least one of my arms, the one on the bottom, would be folded. However, if I fell asleep on my back, I would get the hives on the anterior part of my legs and buttocks. During the day, I might get them under the band of my Apple Watch or, if I wore a belt, along the belt line. If I wore suspenders, they might appear on my shoulders, where the suspender straps went.
Moisturizer seemed, although I was never quite sure, to help. If I applied a moisturizer after showering at night, it seemed that they would be less severe, and if I applied tallow honey balm over the hives in the morning, that not only soothed them but seemed, maybe, to make them go away more quickly. But even without that, they'd generally go away within an hour.
Then, for no apparent reason, there were days when the hives didn't occur, and within a few weeks of that, they stopped altogether, and I still don't know, really, what they were all about.