To instigate a fight, argument, or other conflict. Watch out for those guys. They're always looking to start something with anyone they come across. Hey, man, I'm not trying to start something, I was just sharing my opinion.
Cause trouble, especially a quarrel or fight, as in Stop bringing that up-do you want to start something? [Colloquial; early 1900s]
ˈstart something/anything(informal) begin a fight or an argument: Don’t try to start anything with him, he has a knife. ♢ Are you trying to start something?
To cause trouble.