If it is “logging off” perhaps the laptop is set for stand by mode. That would log out of windows but not shut down the laptop, but I thought the connection would remain active.
He has to move the mouse and the user screen comes up it sounds like the laptop is set to standby…if you set it to “always on” in windows and the standby mode is turned off maybe it is default for the laptop to go into standby after “x” amount of time. Check the Bios see if there is any settings in there.
I forgot there is also a check box that says “On resume display Welcome screen” if your still using your screen saver try turning that off as well.