A new Linux OS may emit unfamiliar sounds if some network app is still running and set to use them for notifications. Quitting the (sound-making) app(s) and/or the network connection will can avoid that problem. Of course you can just turn the sound volume all the way down.
Suspended OSs may sometimes ‘wake up for no reason’ if some vibration causes the mouse, for example, to jiggle around enough.
Logging out of your user account before suspending/sleeping the machine will stop that stuff without having to dig thru settings. Faster to log back in than to reboot.
I’d like to encourage the author of of this to leave the line- and paragraph- breaks in the source text. This is impossible to read as is.