Randomly... At first I thought it might be me hitting the play button by accident or something, but nope I was just sitting here and it loaded up by itself again. It doesn't begin playing anything; it just opens and stays behind the other windows.
A question first : Does it happen when you are in front of the mac or at other times too?
One problem i faced was with the ext speakers connected; My foot was hitting the connecting wire which was dangling, and that seemed to start itunes;
The ext mic or speaker wire if loose, does create this problem.
Other reports have been made with USB Hubs and other attachments;
Un-plug and replugging in your external speakers/headphones seem to work for me. iTunes has a weird tendency of opening randomly if the 3.5mm audio jack is disturbed in a certain way.
Cheers guys, actually that make sense as I just recently replaced the output cable to my amplifier for a splitter cable in order to use headphones too, so I guess that was the cause! 😎