My Phone Keeps Turning Itself Off

It sounds like your battery may be corrupted or bad. You may very well need to buy a new phone to replace it. Make sure of what kind of battery you use. Certain battery types do poorly if they are left on a charger for too long and are best only being charged when they are very low, while other types of batteries work best when they are kept charged and not allowed to run too far down and also work better even while on a charger. Be sure you know which kind you have before looking into purchasing another, so you know how to get the most optimum performance and life from it.