Why does my Macbook Air randomly freeze?

Ever since I first got my Air 2 months ago, it randomly freezes. It usually happens a couple times a week. I will be working on something and everything stops. No response to mouse inputs, no response to keyboard inputs, no spinning icon, just completly frozen. Today I was listening to iTunes, cleaning on the other side of the room and it just froze. Music stopped and it wouldn't respond. I have to hold down the power button to get it to restart. I have reset the SMC and it seemed to reduce the number of freezes, but it still continues. All software is up to date. Any ideas?