1) In the original post I stated that "I do not have any powered-on devices attached to USB ports."  That was false.  The printer was powered on and was attached to a USB port.  Therefore, powering off the printer fixed the problem:  when I was in Windows 11 and clicked Shutdown, the desktop powered off and did not restart, as long as the printer was powered off. 2) But I like to leave the printer powered on (it has a sleep mode).  So I went into the BIOS and disabled the option that allows a device attached to a USB port to start the desktop from Sleep, Power-Off, or Hibernation.  That fixed the problem.  I could leave the printer on, and when I clicked "Shutdown" in Windows 11 the desktop powered off and did not restart. 3) However, this fix created another problem.  It was no longer possible to wake the desktop from Sleep mode by pressing a key or moving the mouse, because both the keyboard and the mouse are attached to USB ports.  Because my wife often stops using the computer for an hour or so, and it subsides into Sleep mode (as set in the Win11 settings), this state of affairs was not acceptable. 4) So I went back into the BIOS and re-enabled the option that allowed a device attached to a USB port to wake the computer from Sleep, Power-Off, and Hibernate. 5) So now the desktop will not shut down while the printer is powered on.  (Actually it does shut down, but then after one or two seconds it starts again because the printer is powered on and is attached to a USB port.)  But my wife can wake the desktop from sleep by pressing a key or clicking a mouse. 6) I wish that Dell would modify the BIOS so that the computer will shut down and stay shut down while the printer is powered on, but will still allow a keystroke or a mouse movement to wake the desktop from sleep.  That is the way that the desktop worked before I installed BIOS 2.12.0.  
Hello,  1. A few days ago (05/18/2023) I installed BIOS Level  2.12.0  on my wife's XPS-8940. 2. Since then, when she does a shutdown from Windows 11, the computer shuts down momentarily, stays powered off for about 1 second, then restarts.  This problem did not occur before I installed the BIOS 2.12.0 upgrade. 3. I can still power off the machine using the power button. 4. Here's how I do a shutdown from Windows 11.  This used to work before I installed BIOS 2.12.0.  Now it causes a Restart rather than a Shutdown.  (a) Press Alt-F4.  (b) Select Shutdown.  (c) The system appears to shut down and power off.  However, after about one second, the machine powers on again and starts up. 5. In the BIOS:  (a) Boot from network card is Disabled.  (b) Boot from USB is enabled, but I do not have any powered-on devices attached to USB ports.  6. Any thoughts on what might be causing this problem?
XPS 8940, BIOS 2.12.0, shutting down Windows 11 causes Restart rather Shutdown