If you plug in the iPhone to a power source (like to charge it), it should turn on.. Unless it's broken.
assuming you let it charge for a while (at least an hour) and the charger is good and assuming that it just turned off by itself (meaning something bad happened)? I would guess the only thing left to do is pay a repair guy or buy a new one?
My ipod is jailbroke but i want to restore it to normal setting but when it powers on it just freezes (also im on a app where it makes your ipod look like a htc) and when i try to power it off it it freezes on the power off screen, also because im on this Dreamboard app i can't access any apps to turn it off another way.
Unjailbreak it so it doesnt freeze and lock up anymore. Follow this link (taken from the page above) for ways to restart it without the lock button best ways to restart an iPhone without the power button
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