Help When charging

When my Samsung s4 is charging it vibrates roughly every 5 seconds as well as lighting up for no apparent reason? Can anyone tell me what's making this happen and how to stop it?!


Thread starter
The phone is charging perfectly, I bought the phone refurbished and I'm using the charger that came with it (I'm pretty sure it is the stock one) and no there is nothing coming up on the screen that would suggest why it's vibrating other than a little eye but I think that means the smart features are on?