Started happening recently.

I have 5 drives in my computer. One of the them recently started disappearing. It doesn't show up even if I restart my computer. When I scan for new hardware in device manager, it shows up only to disappear right after within the next 15 seconds. No errors in event viewer. I have all the data backed up. Its a *data* drive that was being backed up every day to a backup drive before this started happening so I am not worried about losing anything. I am not entirely sure if its a dying drive or an issue with the controller or cable. Any ideas?