Hard to say. Maybe if you provide more info someone can help you figure this out.
Where are you charging it?Plugged into a USB port, using the iPhone charger, on a car charger (which one) or what?
What exaclty is not working? The touchscreen doesn't work, you can't make a call, it acts randomly weird, or what?
First thing I'd try is USB or iPhone charger using the charging cable that came with the phone.
Second would be to try it somewhere else or on a different computer, to see if it is some kind of interference.
Third would be a reset of the phone