[acontrasto]

Do you have email set up in messaging?

There are really many reasons that it could wake from sleep. My first intuition was that anytime email is retrieved, it will wake from sleep. If other apps run in background mode, this may also wake up the device even though it may seem like for no reason.

To give you an example, every morning at 3:30am my phone wakes up from sleep in order to update my contacts with an online server through Microsoft MyPhone. Even though, nothing noticeable is actively taking place on the phone, it is silently transferring the contacts. Same goes for email retrieval. The only way to stop that from happening is to change the settings in the app that is causing the device to wake up, or to remove the app all together.