BB Bold 9700 :: Randomly Shuts / Reboot Is Only 5 Seconds?

On my brother's 9700, he's experienced two random shut downs. He's with Rogers and has the latest OS installed (.743). He would notice that sometimes the phone sort of shuts off by itself. Normally he would keep the phone on standby or lock, but when he'd go to unlock the phone, he'd notice that none of the keys work (screen remains black). Normally the screen would light up and say that the phone is locked, but this doesn't happen. Then, he would hold down the End key for a couple of seconds to power up the phone, only the phone doesn't boot up from scratch. Instead, the Rogers splash screen would appear and it would go directly to his home screen. The phone is only about a week old and is brand new (not refurbished). Is there some sort of lock/standby feature that I'm unaware of that his phone is going into? Has anyone else experienced this?