Q: was using my iphone 4 camera, phone froze, got it to shut down but now wont turn back on. What can I do?

Hi duckygallery,

If your iPhone will not power on at all, the first thing I would suggest would be to make certain that battery has a sufficient charge. Plug in your device and let it charge for at least 10 minutes, then try turning it on. 

See this article -

Charge your iPhone and iPod touch - Apple Support

You should see a battery icon while your device is charging. If you continue to see a black screen, reset your device.

 Restart or reset your iPhone, iPad, or iPod touch - Apple Support

Brett L