Always before I have followed the tutorial quest in the start and saw Alduin doing always the same things. This time I tried to do different, run around the city and tried to find if there's something I have missed. I also tried to leave the city through the city-gates. At that point Alduin became interested about me. He landed next to me and shouted me with Unrelenting Force. When I got back on my feet he landed next to me again and started to bite me. I tried to run away but Alduin was coming after me. He ignored all the npcs who were trying to hit him and just came after me and tried to bite my back. Alduin was acting like a normal dragon does in any battle.

cool! I should try that!

i find it funny that when he shouts at you via unrelenting force, you go into 3rd person mode and you get up with your hands untied yet when you get back up, your hands are magically tied again haha..