Why is my machine turning off and/or the screen turning colours when I transport it?

The machine:

13" MacBook Air (mid 2013) with OS X 10.9.5

Processor: 1.3 GHz Intel Core i5

Memory: 8 GB 1600 MHx DDR3

Graphics: Intel HD Graphics 5000 1536 MB

Storage: 500 GB

Note: The battery and power adapter settings in 'Energy Saver' under 'System Preferences' have been set to 'never.'

My problem only seems to happen whenever I shut the lid of my machine and transport it in my backpack. I very rarely restart/turn off my computer. Within the past ~2 weeks, my machine has been occasionally shutting down after I've closed the lid to transport my computer from work to home. Upon restarting it, there doesn't seem to be anything wrong other than a message that says something along the lines of 'you're computer shut down unexpectedly.' Additionally, a new problem happened last night - my computer did not shut down after transporting it this time, but upon opening the computer my normal desktop image was completely discoloured (in a sort of rainbow colour scheme) and was very glitchy. After restarting the computer, everything returned back to normal.

Has anyone encountered this problem before? I was wondering if something was potentially wrong with the screen or if it was something even more serious?