I hear all sorts of excuses about why people won't witness. The ugliest of all is when "devout people" try and give a "spiritual excuse" like "I wasn't led" or "that's not my gifting". Here is the reality - the Great Commission was issued to all (in the greek that means "all") Christians. When Paul talks about the gift of evangelism in his letter to the Ephesians what does he say the gift is for - "to equip the saints for the work of ministry, for building up the body of Christ" (Ephesians 4:12). The gift of evangelism is for the church, obviously to equip them to share the gospel.
Honesty here is what helps. I think it is good if we humbly come to the table and confess to being scared, not knowing how to, and not caring enough. This was the reality of where I was at when I heard the message "Hell's Best Kept Secret".
Charles Spurgeon said "Have you no wish for others to be saved? Then you are not saved yourself. Be sure of that." He continued, "The saving of souls, if a man has once gained love to perishing sinners and his blessed Master, will be an all-absorbing passion to him. It will so carry him away, that he will almost forget himself in the saving of others. He will be like the brave fireman, who cares not for the scorch or the heat, so that he may rescue the poor creature on whom true humanity has set its heart. If sinners will be damned, at least let them leap to hell over our bodies. And if they will perish, let them perish with our arms about their knees, imploring them to stay. If hell must be filled, at least let it be filled in the teeth of our exertions, and let not one go there unwarned and unprayed for."
There are, in reality, only two times we should preach - In season and out of season.