Macbook pro waking up from sleep issue

I have a 13 inch 2012 macbook pro that I bought about 3 months ago. The issue I'm having is that when I wake it up from sleep by opening the lid the screen doesn't behave properly. Here's what happens:
- screen will turn on but be completely black except you can still see the cursor for the mouse
- after about a second the screen will turn off completely
- clicking on the touch pad or on the keyboard will result in the black screen with the cursor coming on again and then turning off like before

It has only happened 4 or 5 times since I got it, but it has now happened 2 days in a row. Any ideas on what might be causing the problem? I did upgrade the ram from 4 to 8 gb if that makes a difference.

Upgrading the memory shouldn't cause what you're seeing to happen. I would try resetting the PRAM first, and if that didn't work, also reset the SMC. If both fail to cure the problem, make an appointment with Apple and have it checked out. Your MBP is still under warranty.