Some fear witnessing because they don’t feel confident enough in their persuasive powers or their ability to answer all imaginable objections to the gospel.  But the power for evangelism is not in our ability; it is in His gospel.  You may have never imagined that an unbeliever could actually be born again by hearing of Christ from your lips.  But that’s not humility.  It’s doubt, a denial of God’s blessing upon His gospel just because it is spoken by you.  Don’t doubt the power of God to add His blessing upon your words when you speak of Christ.