RHEL 7 Workstation system enters "non-responsive" state about once a week

Issue

• Desktop system (HP DC5700M/Core2Duo) enters a non-responsive state multiple times a week with the average being about once a week.
• "Non-responsive" is vague since it does vary. Always, it won't wake up so I can resume my X session nor can I ssh successfully into the machine, and always the disk is just pounding away hard. Sometimes, it is still pingable, sometimes not.