@KSonosD - I’m glad I’m not the only one having this issue. When I first posted my frustration about rebooting without any indication, I too had lost work. And the issue is still happening to this day as there has been few updates since then. 
It’s the only program I know which reboots without notice. Very poor form by Sonos. 

Strange that it doesn’t cause a reboot on my system. Do you have any settings causin this behavior?

Hi @106rallye, not that I’m aware of.  I just launch the Sonos program/app,  then Manage … Check for Software updates etc.  I forgot that this app has rebooted without a prompt before, stupidly chose to update and, unsurprisingly, it downloaded the update and restarted my PC.  It’s been a while since I’ve used or updated it, maybe major releases or changes force the reboot?  I didn’t check what version was installed prior to doing the update.  I’m used to all other software updates, during active hours, on this system prompting if a restart is necessary, so this does behave differently for some reason.