You could have a poor connection at the batterry post/ cable clamp. You could have a strong battery acting like it is weak. If this were the case, using jumper cables would by-pass the poor connection and provide for a normal start.

Check connection quality at the batterry post/ cable clamp with a voltmeter while cranking the engine. You should have a very low value. A high value will indicate a poor connection. Just place one voltmeter probe on the post, the other on the clamp and have someone crank the engine while you observe the value.