This is so annoying, has nothing to do with S3. I have a Fitbit and the dang phone vibrates when BT discounts. It was driving me nuts because the vibration happens but no notifications what so ever. Took me day to figure out why. This was happening on my Note 8 and now Not 9. I turned off blue tooth for couple days to test it and not a single vibration after. So annoying. Don't want the phone to vibrate.