Macbook Air making weird noise

I opened my Macbook Air today and its making a strange noice, kind of like a cross between a CD trying to access data and a hard drive dying. The strange thing is the Air has NO optical drive and the hard drive is SSD.

This is not the first time its done this. I had done it once or twice before. Everything works fine otherwise and after about 2 minutes the noise is much less.

What could be wrong ?

Macbook Air late 2008 13.3 inch

1.6Ghz Core 2 Duo - 2GB RAM

128GB SSD

OS X 10.6.8 Snow Leopard