Haro, I really have no clue why my phone is doing this, but when I hover my hand over the front camera the entire screen goes black for a sec, then back to normal. Does anyone know how to fix this?

 

Is there a motion setting in your galaxy s4 where you can check to see what kind of stuff you got activated?

If so, check to see which one that is making your phone lock and uncheck it. If there isn't an option to uncheck it, then if I were you, turn off the entire motion sensor. I don't normally use motion since I find it a waste for me. I don't have s4, but I got s3, so I somewhat kinda understand your phone a little.