And you are turning it off from the quick setting menu? How many devices do you have paired, maybe try unparing all the devices, then turn off bluetooth. I have not heard of an issue like this one before..
Check your apps if any of them have permission to turn your Bluetooth on than they can. Do you have any app like like samsung pro or any other which manages your Bluetooth device? If this doesn't help, go to setting and reset network settings. That should fix your problem.
