Phone vibrates on its own

[Dimisarta]

Last couple of days i have noticed that my phone vibrates on its own while the screen is off.
I checked again and again whether this is caused by some apps or email or anything but that's not the case. It just vibrates for a sec and then stops.
Any idea someone what's wrong? Anyone has faced the same ?

 

[ingbrzy]

its vibrating when you plug/unplug into changer and USB..

 

[Dimisarta]

No no .. this happens on its own. Not while connecting or disconnecting anything.

 

[imortalitzik]

its vibrating when you plug/unplug into changer and USB..

Can i deactive this function that it vibrates while i am connecting and disconnect it from charger ?