why does my mac book pro restart when i move it

Hello All,

I had purchased my Mac Book Pro in the Summer of 2011 just before i went off to college. This past year i have had problems with the laptop restarting completely whenever i move my laptop or often it "quits unexpectedly" I have been avoiding this problem due to the fact it started happening more and more during finals week. Its running on OSX Yosemite 10.3, 6 GB of memory, 320 GB storage, and a processor of 2.3 GHz intel core i5.

It seems to work whenever i keep it stationary, but as a college student it is required for me to take my laptop my laptop to classes to take notes, or not take notes ;p.