I had a similar problem. It got so bad, Itunes was popping up every 15 seconds. My operating system is Windows 7. I wondered if simply uninstalling and reinstalling might solve the problem. I went to Control Panel, opened Uninstall a Program, clicked on Itunes and saw 3 options: Uninstall, Change, and Repair. What the heck, let's try Repair. It worked! Itunes has stopped opening up on its own. Nevertheless, I have my fingers crossed.
Having this issue as well and I don't sync my phone/ipod/whatever. I've unchecked all the things this thread and other similar threads have advised, and it's still doing it.
I've noticed that when my bluetooth speakers automatically connect/disconnects, this might be a trigger for zombie iTunes. Do any of you have bluetooth enabled and noticing the same?
Would love to find a resolution to this (besides uninstalling iTunes... next step).