These lines have an about 50% chance of showing up after my iMac boots. If I restart my computer 1-3 times it will go back to normal, which is odd. The lines slowly wobble. I've searched and found other problems with odd colors, but nothing similar to this. My iMac is an late 2012 model, 10.8.4 2.9 GHz Intel Core i5. Help is appreciated.