My iPhone 5 froze after the YouTube app failed to open.
I've tried holding the sleep/wake button + home button down with no luck. Nothing happens. I'm able to slide down the Notification Center and type and search in the box but then I try to open an app and nothing happens.
If I press and hold to activate Siri, she appears for a second then turns off as if I pressed the home button again.
I've tried connecting the iPhone to a Mac but as it's passcode enabled it tells me to unlock it and then replug it which I'm not able to do.
Best Answer
If Siri starts but then stops "as if [you] pressed the Home button again", I'd say there might be a problem with your Home Button. Try using the Apple earphones with volume/play control and use that to press Home button for Siri. Does Siri still behave the same way?