Why does my iPhone vibrate for no reason?

Unlikely it's vibrating for no reason. Most likely is an app that's trying to tell you something. Check Settings > Notifications and see if any of the listed apps are trying to notify you.

FINALLY figured this out after 2 weeks of searching. I had removed everything from my notification center and turned off all notifications in every app. Do this:

• Settings ->
• Sounds ->
• New Mail (or whatever you think is causing the vibration) ->
• Vibration (then scroll to the bottom) and click 'None'

Very strange that to turn off a vibration you would have to go into "Sounds" instead of the notification center, but it worked for me.

You may be receiving these vibrating alerts even if the notifications are turned off.

Note: using iPhone 5C, iOS 7.1.1

FINALLY figured this out after 2 weeks of searching. I had removed everything from my notification center and turned off all notifications in every app. Do this:

• Settings ->
• Sounds ->
• New Mail (or whatever you think is causing the vibration) ->
• Vibration (then scroll to the bottom) and click 'None'

Very strange that to turn off a vibration you would have to go into "Sounds" instead of the notification center, but it worked for me.

You may be receiving these vibrating alerts even if the notifications are turned off.

Note: using iPhone 5C, iOS 7.1.1