Samsung SGH-T809 / SGH-D820
t809 powers off solo
I don't know how often it does it, but its enough where every once in a while i see the start-up screen come up.
I called up T-mobile yesterday and they said that they did not have any reports of this happening.
Before they do an RMA on the T809 they had me do a master reset. They said keep an eye on it and call them back if it still happens. Previous to the call to them I had the start-up sound disabled, but I enabled it so I could better track if it happens again.