The first thought that occurred to me was dust. That has already been suggested, though. Would you be willing to do a factory recovery to the factory image? That would determine whether this is a hardware or software issue. Perform a Complete Restore
Otherwise, for a 1/2 year old laptop that has a non-removable battery, my suggestion would be to use the warranty, in which case they will do the recovery for you, so really it is worth doing yourself to test. This may be a hardware problem that is graphics related.
Backup any important data to an external drive or USB flash drive prior to doing either of the above.