That happened to my Challenger too. It was the battery. Just put it on a charger and it will start up and be fine.

69 Super Bee 440 5-speed
70 Dart Swinger 340 4-speed
69 Camaro SS 396 4-speed
66 Cutlass Convertilbe
70 Judge Ram Air III 4-speed
68 F-100 SWB