The Surface Pro 3 will frequently wake up from sleep spontaneously, with no
user input. Often this happens when it's in a case or bag, so the user might
not notice.

If you have your Surface set to not auto-sleep as quickly as the default, it
can heat up in the bag. It's likely that all Surfaces do the spurious wakeups,
but that the default inactivity sleep of "almost immediately" hides the
problem.

These are wakeups are apparently caused by Bluetooth  turn off Bluetooth and
use hibernate instead of sleep (because in sleep mode, just touching the area
of the screen around the windows logo will cause a wakeup. If the Surface
brushes against anything capacitive [like a headphone cable] in the bag, this
will cause a wakeup).

Note that Bluetooth is not needed for the pen to work.

To make a "hibernate now" shortcut on the desktop, make a file called
"hibernate.bat" containing:
shutdown /h