Samson was chosen before he was even conceived. He had no merit, no skills, or knowledge. He wasn't chosen to be the judge of Israel because he was a righteous man, but because he was the man God needed for the job. If God calls you to a task, don't argue with him and don't fear your own weakness. His strength is sufficient for you to carry out his will. He knows what he needs. You don't.
Just like Sarah and Rachel centuries earlier, Samson's mother wasn't barren because of sin, but for God's glory. God's decision-making process incorporates wisdom and knowledge that we could never comprehend.
Judges 13