Sounds like CD/DVD resetting after inactivity

I just got my MacMini and it is almost too quiet. Although after about every 10/20 minutes of inactivity I hear a noice that sounds like the DVD/CD resetting or tyring to load a disk.

I am still doing the majority of my work on a PC with the Mini on a KVM, so I am at the desk and typing on the PC and hear this noice form the Mini - any ideas?

I'm not sure, but it might what it is supposed to do. If it is not affecting your work or performance I wouldn't worry too much about it.