I have a pitched roof with, I guess, asphalt shingles.

A few weeks ago, water was dripping from a spot in the 2nd floor
ceiling, during the rain.

But the rain was ending when I woke up, and it's rained several times
since then, even more heavily, with no dripping.

Not positive but I don't think there was much wind when it was dripping.

What's going on?

What should I look for when getting it fixed?

How can this be?

Why did my roof stop leaking?

The drip was only a foot from a 12" stovepipe fireplace chimney, hidden
in the walls, but on the roof that has a metal collar around it, and it
was sealed properly around the base of the pipe.