Flashing? mark folder on startup + random freezing

When I start up my MacBook Pro Retina (Mid 2012) I very often get a flashing question mark folder on startup. I can still get the machine to start up and function although it won’t be long before it freezes the whole system and I have to force shutdown. When I turn on the MacBook again the dreaded question mark folder re-appears. I believe this has something to do with the ribbon connecter to the hard drive. This looks like an easy fix for earlier machines but with the unibody and retina 2012 (and onward) models I can’t seem to find a tutorial walk through and what replacement ribbon connector I need to buy? Any help would be greatly appreciated!