Hello and welcome.
I doubt it is a virus, as I have heard of this issue before. Some of the causes/fixes that I can remember:
-If you have external speakers connected, and the jack is a bit loose, it can trigger iTunes to randomly playback
-Uncheck Prevent iPods, iPhones, and iPads from syncing automatically in iTunes > Preferences > Devices
-If you have an Apple Remote paired and its battery is dying or the button is accidentally pushed (it is under some papers for example)
-You could try deleting iTunes Helper for Login Items
-You are clicking on iTunes links on web pages
-There is a custom keyboard shortcut
There are a few others, but see if any of these help.
C