God sent Paul and Paul found out how much he would have to “suffer for the sake of Christ”.  Paul feels “compelled” to preach because he is an Apostle, one who is sent.
I have been going back and studying Romans and I am constantly confronted with this “decision theology” that lurks all around.  It is in all of us and hard to get rid of.  We want to contribute to salvation.  I was struck by Romans constant refrain that it is all the “power of God”.  God send His Word, He sends  His Son, He sends His Spirit and He sends preachers.  God is the sending God.
Romans 10:14, “How, then, can they call on the one they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear without someone preaching to them?” The assumption is that if one is to must be preached to in order to believe, then one must also make a conscious decision to believe. Luther takes a different approach to the interpretation of this passage, focusing on where the process ultimately begins. “These four points are so interrelated that the one follows upon the other, and the last is the cause and antecedent of all the others, that is, it is impossible for them to preach unless they are sent; and from this, that it is impossible for them to believe if they do not hear; and then it is impossible for them to call upon God if they do not believe; and finally it is impossible for them to be saved if they do not call upon God. Thus the whole root and origin of our salvation lies in God who sends.