If it was the flywheel, wouldn’t it squeak continually, though, and not just when idling+cold?
I know I should probably know more than I do...but at the same time, I know how lousy I am with hardware in general, so I hesitate to really delve into it. I might be able to speak with more authority, but I still don’t think I’d want to do the actual work. Not on something that’s liable to kill me if I get something wrong...
OK, I must not have been paying attention to the timing of the squeak, or is it a squeal? My van was squealing for a while. It would happen when I first started rolling, but then would stop as the van warmed up, or when I applied the brakes, so I knew it wasn’t the brakes. Turns out, it was a loose caliper on one of the brakes, and it wasn’t that expensive to fix.
Cold temperature could cause the flywheel/shaft to shrink at different rates which is why you only hear it when it’s cold outside.
The speed thing may be caused by the engine being older and hitting the right vibrations at idle/lower speed to set it off, then once you go faster the vibrations change frequency and the squeal stops.
Get a can of WD-40, cheapest way to find out if that’s it.
I’m a jackleg mechanic who did not stay at a Holiday Inn last night but I did drive a few 10+ year old cars for a decade until a bought a new one last year.