Car tries to merge into me after driving inconsistently

So I’m driving home from work, and I get stuck behind this guy who’s speed is all over the place; anywhere from 25-50. We get to the traffic light and he goes to turn right - I’m going straight - then he changes his mind tries to come back into my lane. Right into me. He never swerved or braked to avoid me, either! Just sat there next to me on the bike lane. After the light changed, I went on my way and he disappeared behind me.