I have a SGH-G600 slidephone, at 15 months old, light use, developed random charging faults and would power off and refuse to power on.
Tried another compatible Samsung charger and new battery but eventually found if I twisted the phone very gently it would behave for a few minutes or hours. (hold phone and imagine unscrewing a jam jar lid)
ie dodgy connection or Motherboard joint.
I wouldn't recommend you try anything of the sort (danger of cracking the screen)
Take it back, it's under warranty.