Heat! Heat may be your problem. I have been repairing coputers for 38 years of various types. I find that it is quite common for laptops to accumulate
debris inside that blocks adequate airflow. Download and install this free utility "Coretemp. http://www.alcpu.com/CoreTemp/ You can use it to see if your CPU is getting too hot and take action appropriately. A short article on the subjetc can be viewed at http://www.bestpcfixit.com/forum/laptop-freezes .