2003 V6 Electrical

[Hayden238]

so I'm new to the forums and I have a very odd problem I have never experienced and I need help, I have a 2003 mustang that is having electrical problems first I'm going to start with the car won't go in to gear unless the headlights are on, next when in drive(auto trans) once you hit about 25 mph when it try's to shift to 3 rd gear it slows down drastically feels like brakes are locking up you can tell its electrical but I have no idea what it could be help please