Hi. My kitchen refrigerator (GE Hotpoint) started making an odd
noise this morning. From a distance, it sounds like a hissing
sound; but when you get closer, you can hear that it's actually
a high-frequency clicking or flapping (maybe 20 or 30 clicks/second).
It appears to be coming from the back of the fridge, and it only
occurs when the compressor is going; when the fridge is otherwise
quiet, the sound isn't present. There's been no impact yet on the
fridge's cooling. The fridge does not have an ice-maker.

I'd almost guess that it's simply some piece of paper or whatever
sticking into a fan; but I don't know why this would start this
morning. There hasn't been any activity around the fridge in the
last couple of days that would afford the opportunity of something
falling back there and getting into a fan. Pulling the fridge out
of its cubbyhole is a major endeavor; I'd almost have to call
the appliance repair people for help just to do so.

I'm wondering if people have some plausible diagnoses for what this
might be other than just some piece of paper sticking into a fan,
so that I'm a tiny bit more educated if/when appliance repair people
come and tell me it's going to cost 18 bajillion dollars to fix.
Given that the refrigeration doesn't seem to be compromised (yet),
does it seem likely to be an ignorable thing, or is there a good
chance that someone needs to look at this right away?

Thanks for any info. Sorry, I'm pretty ignorant about refrigerators.