Finally! The following worked for me I am running macOS Montery 12.3.1 on the base version of Mac Studio.  My situation: This eject thing was happening to me repeatedly sitting idle as well as running a production php to process videos and photosets for release on my website.  This program can take 10 to 30 and more minutes easily depending on how many videos and photosets I process. I have an older Fideco docking station that had been hooked up to my 2013 iMac.  In this dock I have a 10TB hard drive and a 480mb SSD. This particular dock uses USB A to connect to the CPU.  I need to use a USB extension cable because the docking station can not reach either the the Mac Studio or iMac based on my placement of stuff on my desk. So, I connected the extended USB A cable from the Fideco dock to a USB A slot on the back of my new Mac Studio.  I would run my production program and EVERY single time I would get disk eject msgs for each volume stored on the Fideco dock.  I would even get the eject msg with computer idle.  My solution: I read the comments on this thread how it might be a power issue.  So what I tried that is still working with NO eject msgs is: 1) Attached the extended male USB A from the docking station into a short USB A to USB C Apple cable.  2) plug the Apple cable into a USB C slot on the back side of the Mac Studio.  3) In the System Energy Saver prefs I checked “Prevent your Mac from automatically sleeping…” and unchecked “Put hard disks to sleep when possible”.  Aside from the preference settings, I suspect it was the connection from my dock via USB A to USB A that was the problem (perhaps also the use of the extension cable).  Just finished another run of my program — took 40 minutes.  Also took 10 minutes or so to write this text.  Still, no eject msgs! Still use the original USB A cable and extension. Now, however, I plug the USB A into the short Apple USB A to USB C cable and then the USB C into the back of my cpu.