Sony xperia m4 aqua will turn itself off and on, it won't work wifi.

I have a Sony xperia m4 aqua phone, the phone in February will be 2 years old. For some time it has lost wifi and either does not show any available or to work and be connected you need to turn on and turn off the phone, which sometimes results in the fact that it turns on after a few minutes only, it is also that the wifi is "hanging" or like moments of division shows that is connected but the internet does not work. If I turn on any application, e.g. instagram, facebook, then the phone turns itself off and on.

Initially restore the factory settings. But I'm afraid the CD is raining. A common malfunction in this model.

Restoring factory settings, unfortunately, did not help, when it turns off the phone takes a lot of battery.