CD-RW Spins up without CD in?

I turned on my computer and the CD-RW started spinning up like it is reading a CD but there is no CD in it. It makes my laptop vibrate like a big cell phone. It has done it three times so far at random intervals. Does anyone have any ideas why this is happening and how I can stop it.

Thanks in advance,
Clint

Get some canned air and blow into area inside the drive bay. Could be just some particle interference, or not since it is intermittent, but I would try that. Otherwise it could just be a seek related to last action prior to shut down. See if you can repeat it by having a program going that occasionally seeks off the CD drive and then removing the disk and shutting down without first ending that program and then powering up.

Well it turns out it was not the CD-RW spinning it was my harddrive So I can only see two possibilities. 1. it is loose in the case and all I need to do is tighten it or 2. my harddrive is dying I won't have a chance to look at it until lunch. Thanks for the suggestion though.