Apple Wireless Keyboard not connecting automatically on wake

Solution 1:

Resetting the SMC should be able to fix the issue. Note that this will reboot the MacBook, so you will lose any unsaved work.

• Shut down the computer.
• Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
• On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
• Release all the keys and the power button at the same time.
• Press the power button to turn on the computer.

Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.