Why does it turn on its own?

[Genjinaro]

The following helped me stop it.

Update to 2.17 ROM
Call *2 and ask for the "latest PRL update"
Go to sounds & notifications in settings and deactivate anything in the connection established section.

Stop ActiveSync from running (Usually this is > "WHY?!" so look out for it.)
Fully close PIE, Opera & IM apps
See what apps auto update and if they wake up the device.

Hope this helps..,..