I recently picked up one of the older Central Machinery 12" disc sanders from an estates sale for cheap. It has a weird, intense vibration for about a half second during startup. Once it's running, it runs nice and smooth and works well. When I turn it off it coasts for forever, but doesn't seem to have a vibration during slowdown.

Is that just some centrifugal switch engaging/disengaging? I'm wondering if a bearing is on its way out. Unfortunately my Googling is only bringing up threads of people who have vibration while it's running, which isn't my case. Obviously this isn't a really nice sander, so if that's just how it's built I can live with it.