Why won't my screen come up when my computer comes on?

When I open my macbook from sleep or turn it on the screen comes up with a bunch of different colors. Like all the little lights in the screen will be different colors. It will slowly fade to all white than the normal screen comes back up. After this the screen will flicker and be very laggy. Then that to will after a few minutes go away and my computer works normally again.

PLEASE HELP ME!

I have a late 2009 Macbook 2.26 GHz Intel Core 2 Duo

2 GB 1067 MHz DDR3

Software is 10.8.5