iPod – occasional warning messages about "restoring" when ejecting, then a wiped iPod disk.

My 120mb iPod was bought used about 4 years ago from someone who themselves barely knew how to use it, so got no guidance from the seller to help me get started. Since then I have used it only for music and podcasts.

On occasion, when ejecting the iPod from my MacBook Pro, there is a warning message about "restoring" the device to factory settings. No explanation is given. This has happened maybe 5 or 6 times in the past two years.

"Restoring to factory settings" implied iTunes would erase the disk, which I didn't want. And no explanation was provided for why the device needed to be restored. Not fully understanding this, I've somehow been able to eject the iPod and use it as before. On a few occasions, the iPod seemed to reboot itself after I had properly ejected it, displaying grey screen with Apple logo before opening into the familiar screen.

All of this has seemed erratic and variable, for no discernible reason. The random behavior has been puzzling and a little concerning. But the device seemed unchanged through all those warnings.

Until yesterday... After downloading a podcast and moving the file to the iPod, and waiting until I was sure the transfer was complete, I "ejected" the device just as before. (Battery level indicator showed nearly full charge). This time, the result was different.

ITunes displayed an unfamiliar and larger alert message, offering me the choice to "restore" or eject the iPod. Again, I chose eject in the warning message I saw on the iTunes screen.

The result was that ALL my saved music and podcasts had been cleared from the iPod – no files under music, or podcasts.

Eventually, after an agonizingly long and useless chat interaction with Apple Support advisors, followed by an equally worthless encounter with the local Apple store, I found online ads for iPod repair to inquire about "repairs" and called the nearest store. That was equally unproductive.

The second Apple chat advisor settled on the idea that there was a bad sector on the iPod, or some other defect he was unable to explain in language I could understand.

I've now manually moved a few podcasts to the iPod. They play normally. I have also moved a couple music playlists which also play. So the device is still functional.

The independent repair shop referred to a way to use some procedure to transfer the music playlists without doing it "manually" but I've not yet found instructions for that.

So the questions:

1. Why does this iPod intermittently behave abnormally, and want to be "restored"?
2. What should I do if/when iTunes presents me with the warning about "restoring" the iPod?
3. Is there something deeper that needs to be done to the operating system in the iPod to resolve this? And should this be attempted at an independent repair business?
4. Is it more likely now that iTunes will repeat this clearing of the iPod hard drive?
5. What is the smart way to move my music playlists from iTunes on my two Macs to the iPod?

My current Macs are all very old. MBP is 2011 (High Sierra), MacPro is 2012 (Mojave). Yes, I AM intending to to replace both in the next few months.

Thanks in advance for any and all suggestions.