In article ,
Jon Elson wrote:

Had two circuit breakers do something odd at home. One tripped, and I
assumed somebody had a space heater and a hair dryer on at the same time or
something. Then, a breaker for my computer room tripped when I turned on a
laser printer. No unusual loads that I haven't done a hundred times before.
I unplugged the laser printer, thinking it might have given up the ghost.
When I reset the breaker, it was noticeably warm, which seemed odd, as it
was not feeding a heavy load. The laser printer and everything else was
just fine.
It took a couple hours for the breaker to cool. I can't remember for sure
if the breaker that tripped earlier had also been warm, but it might have.

Is this a plug-in breaker, or one that's wired in?

In either case, it seems possible that its connection to the wiring
has deteriorated (oxidized, worked loose, etc.) and it might be
heating up at that point. If your home has any aluminum wiring, I'd
be _very_ concerned about this possibility.

I'd recommend a full re-check, with the mains power entirely
disconnected.