I'm not going to say that the TO bearing couldn't cause this, but usually if a TO bearing is going out, you are going to get noise any time the clutch is in. Seems strange to me that a TO bearing would only make noise when you first let the clutch out at the start of the day, and is fine after. Sounds to me more like you have something going bad in the tranny (like a bearing?), and once everything rotates a few revolutions inside the tranny, it gets lubricated and the grinding stops. But, that's just a guess. Or maybe something is rubbing (clutch disk? flywheel? pressure plate? driveshaft?) when you first start and causes the grinding, but I would think that would happen more often during the day.

Maybe you could park the car at the end of the day with the rear wheels up on jackstands. Have a friend start the car the next day while you are lying beside it (NOT underneath it - we don't need to read about you getting crushed) and release the clutch, and see if that gives you any clues as to where the grinding is coming from. You might be able to pinpoint that it's coming from the bellhousing area, or the transmission, or the driveshaft. Unfortunately, from you're description, you will only have one chance per day (and a short one at that) to troubleshoot this...