Motivational speakers often say that to be successful, we need to visualize our success in advance: a corner hi-rise office, promotion, sale of a business, running a marathon, etc. And for lectors, this exercise can also bear fruit.
Fr. Michael Sparough, in his lector training program, This is the Word of the Lord, suggests doing "presence" exercises; by imagining our "best self" standing in front of us with the light of God's love shining on our heads, watching the words go forth from our lips, and warming the hearts of our listeners.
As we visualize this "best self" of ours, we need to step into it from our usual self and feel the change. It's a visualization we have to create, and then build the confidence to become the fullness of that visualization.
Another exercise is to imagine yourself washing the feet (figuratively) of your listeners with God's word. Imagine the humility and love that Jesus showed as he actually did wash the feet of his apostles. Work at proclaiming your readings with this same humility and love, and you'll begin touching many more of your fellow parishioners' hearts.
Along with these exercises, imagine Jesus as your coach; standing beside you with his hand on your shoulder, guiding and encouraging you through your reading; and you'll soon develop all the confidence you need; never being discouraged by the few who talk or doze while you're reading; and always knowing that there are many more people who are hungry for God's word and waiting in anticipation to hear you.