SMC reset. Random system freezes, and unresponsive keyboard & touchpad after plugging USB device

Lately I had some problems with my macbook air. Random system freezes, and unresponsive keyboard & touchpad after re-opening the lid.

I first tried a memory diagnostic (by booting pressing 'D') to discard a memory fault, but the RAM was OK. After surfing the web I found that I may have been needing to reset the SMC (System Management Controller). So I did, it but in the end the system continued to randomly freeze after plugging some USB devices.

Reset Macbook Air's SMC

1. Shut down the computer 
2. Plug in the power adapter if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Reboot as usual.

The procedure for other Mac's is slightly different, so it's better to look them up here or here.

Solution to unresponsive keyboard & touchpad after plugging USB device

In the end the culprit of this behavior was the android file transfer tool. What solved my issue was to disable the autostart of this application.