Make sure the screen is clean and then do a hard reset. The issue may also be because you have too many apps running and the system resources are slow to act (had this happen to my phone many times) A hard reset will help with the slowness.. See the link below for more information. http://teachmeios.com/how-to-hard-reset-your-ipad-iphone-and-ipod-touch/
Four possible solutions
1. Remove the Sim Card & Throw the phone away in a recycle bin.
2. Cover the glass with a new screen protector & ignore crack.
3. Take the iPhone into an Apple centre & pay a modest fee to get the next model up (4s) which fixes the problem & gets you better technology.
4. Get a new glass & replace it yourself. Parts & repair guides are numerous on the net. eg. See www.youtube.com/watch?v=qhgvXO1wXfwIt never ceases to amaze me the number of people who bust their Smartphones. Some even regularly.
My son-in-law has dropped 2 in the water while fishing and he should know better as he is a radio technician.
You need to treat this amazing modern technology with respect!
Personally.... I have never broken any of the iPhones I have owned since 2007 and I change phones every 2 years & my wife gets the older technology. So thats 7 years & 4 iPhones!
Perhaps its because, over the years, I have repaired so many electronic/electrical devices.
I do have my phone on me all the time (except when fishing & diving etc) in some pretty harsh environments (e.g. fixing cars & prospecting in outback &... I have chipped the edge of one phone).
I have a respect for my expensive technology and that it has a large flat glass area that pressure or knocks can break. I just take 5 seconds to think ahead as to where I will be using it & I keep a silicone cover & screen protector on it at all times. I move it from my top shirt pocket to my front jeans pocket if bending etc. and the screen always stays on my body side while in the pocket.
Press home volume down and power when phone comes on take finger off power then volume then home. plug into itunes and restore software after it has installed click on. re put on the last saved from list and this will restore phone to your last saved info.
First: are you doing a jailbreak?If so, download " TinyUmbrella" : http://blog.firmwareumbrella.com/Second: connect youe iDevice to your Mac or PC while in the recovery mode.Lastly: give TU a few secongs to recognise your device and then click on " exit recovery"tada!
Hold down power button for 3 secs then hold down home button without releasing power button for 10 seconds then let go of power button and hold on home button for 15 seconds. Device must be turned off and pluged into itunes. then restore it
Do you mean that it won't turn on?
Is the battery full?
Does it do anything when you connect it to a charger or to a PC?
Try holding the power and the home button for some 20 seconds, or until you see the Apple logo, if it ever turn on.
The iPhone is just like a computer, it crash like a computer, it goes to safe mode like a computer. Maybe it crashed. Now, please let me know so I can follow up and help you in any way I can.