I'm not so sure about that. If he was looking for trouble, wouldn't he have had his gun already out of the holster? Why keep it in the holster until he's on the ground being pounded if he was hoping to shoot the kid? Sounds to me like he was tired of people stealing from his neighborhood and wanted to make sure this one got caught, so he followed. The kid didn't like being followed and jumped him.
The pressure of the trial, death threats, etc. may have made him a little crazy since then, but I still don't think he went looking for trouble in the Trayvon case.