Is someone tracking my iphone?

I have an iphone 4
sometimes the little grey arrow will randomly appear for a few seconds for no reason
does this mean someone is tracking my iphone?
would it be possible for there to be any way of doing that even if they don't have my icloud password?

The little grey arrow at the top of the screen tells you that GPS is being enabled and used. This can be controlled by applications you may have installed which search for your location. It may be possible for people to be tracking your iphone. To make sure, go to your settings and disable GPS tracking on all of your applications, including the camera. If this still occurs you should contact Apple immediately.