Dear Michael,

Be not afraid!

These are Christ's words, repeated continually by our Holy Father.  We have to pay attention to him.

Besides, it is amazing the changes we can work in our lives when we are sure God is asking something of us. I see it over and over again. The shyest, the most unlikely persons become true and convincing apostles when they realize it is not their work and qualities but God's truth and grace working through us that obtains the fruit.  

Speak to the seminary directors. They better than anyone else will be able to tell you if your quietness and introversion are within the normal range or if they would really be an obstacle to being a priest.

God bless.