Before dying in the fight the first time, the ender dragon was behaving normally but once I got back, it circled around the end at one height, no longer shooting the fireballs or swooping down to attack me. I tried to build up to swing my sword since I ran out of arrows, but I kept getting launched when it passed, unable to do any damage and nothing seemed to fix the dragon. I ended up getting more arrows and finishing it off that way.