First check, whether charged phone. Often mobile devices are discharged at the most inopportune moment. Thus the cell may not turn on if charge left. You need to charge the phone, that he was involved. To do this, insert the charger plug into the phoneand into an outlet.The phone itself off due to a failure in the software. As practice shows, a reboot of the device will not help here. You need to reflash the phone. For that on the Internet, enter the model of your phoneand request the firmware. Also download a software that is designed to perform such operations. The Internet also has detailed instructions that explain in detail how to reflash the mobile phone. If you do not know how to carry out the firmware, put the phone to your nearest support center. You, for a fee, will update the version of the software.A mobile phone may turn off automatically when a large sub-zero temperatures. In the statement, which was along with a phoneohms specified at what temperature you can use the device. It is also worth noting that the device can be turned off simply due to wear and tear. Usually the cell is usually no more than 4-5 years. If your mobile phonehave around for so many years, it is time to buy a new one. At this time the cheapest phoneyou stand from 500 roubles. The firmware of your can is much more expensive.If you still don't want to change your phone, and there you have important contacts, take it to a shop. For a fee, and you will fix the machine. However, it should be noted that not every master will undertake such work as spare parts for older phoneyou find quite difficult, and the whole work will cost a lot.