[CentOS] Centos Freezing

Hello,

For some reason at different times Centos will freeze and not allow me to do anything. This doesn't happen while I'm working on the system but after I have locked my session and then return. It could goes days without a lockup and then the next time I try to log in it'll be frozen.

I would like to know if anyone else has seen this or knows of a fix or where I could start to look to find out if there is a process or something causing this.

I normally have the same programs running so I don't think it could be caused by me starting and then leaving something new running.

Thanks for your help.