If you are taking the computer out into the heat of the day via backpack or such,
THAT is NOT a good thing for the LT, the LCD screen,  and especially not good for Li-Ion batteries.
(I) would recommend that you create a sleeve out of water heater insulation material and Duct tape.... REALLY!

  The kind like in the picture.
  you can get it at Home Depot and it is a good insulator.
  Just cut into a pattern that can be wrapped around you LT and create a pocket sleeve with duct tape.  They have MANY different PATTERNED tapes at Home depot too.

It will keep the heat from penetrating into the LT as quickly.


There IS the possibility that you have BAD hardware too. 
IF your laptop is a DELL, they have extensive troubleshooting available on their support website (free)

http://www.dell.com/support/home/us/en/19?c=us&l=en&s=dhs