Final answer:
When Windows 10 wakes up on a tablet without a keyboard, the Start menu opens in tablet mode, optimized for touch screen use.
Step-by-step explanation:
When Windows 10 wakes up on a tablet without an attached keyboard, the Start menu automatically opens in tablet mode (full screen) to work better with a touch screen. The purpose of the tablet mode is to make the operating system more touch-friendly when the physical keyboard is not present. This mode enhances the user experience on touch-screen devices, adjusting the interface for easier navigation and use with touch gestures.