Acts9,20 At once he began to preach in the synagogues that Jesus is the Son of God. 21 All those who heard him were astonished and asked, Isn't he the man who caused havoc in Jerusalem among those who call on this name? And hasn't he come here to take them as prisoners to the chief priests? 22 Yet Saul grew more and more powerful and baffled the Jews living in Damascus by proving that Jesus is the Christ. 23 After many days had gone by, the Jews conspired to kill him, 24 but Saul learned of their plan. Day and night they kept close watch on the city gates in order to kill him. 25 But his followers took him by night and lowered him in a basket through an opening in the wall. 26 When he came to Jerusalem, he tried to join the disciples, but they were all afraid of him, not believing that he really was a disciple. 27 But Barnabas took him and brought him to the apostles. He told them how Saul on his journey had seen the Lord and that the Lord had spoken to him, and how in Damascus he had preached fearlessly in the name of Jesus. 28 So Saul stayed with them and moved about freely in Jerusalem, speaking boldly in the name of the Lord. 29 He talked and debated with the Grecian Jews, but they tried to kill him. 30 When the brothers learned of this, they took him down to Caesarea and sent him off to Tarsus. 31 Then the church throughout Judea, Galilee and Samaria enjoyed a time of peace. It was strengthened; and encouraged by the Holy Spirit, it grew in numbers, living in the fear of the Lord.

At once - He is not waiting for what ever: Paul immediately starts to preach. After all what happened before is this amazing for me. He killed, arrested, persecuted only days before. Now he is preaching with faith and passion! - Often, when i realize i sinned. I go down. It takes some times to start to be confident in God again, that i am forgiven and he is with me. It takes some time, till i believe again, till i am full of the holly spirit again. After all what Paul did i would be slow to start preaching.
Maybe he saw the need of someone like him, who is able to use the scripture to show Christ in a most obvious way.
I am just very impressed about Paul's character here: Need to learn more about him. What about character - can i learn to have a different character?