I keep getting asked for my Apple ID password?

When I go on my iPhone, every few minutes I get a pop-up asking me for my Apple ID password, even though I haven't signed in to it.
I'm worried that someone's trying to hack my account, but maybe it's just a glitch?
Any help would be much appreciated.

Whenever you install a new app or update existing app(s) you get asked for your apple ID and password. That's just normal routine.
In your case (and in mine too) the dialogue box appears after you have left the App Store.
Three words for you… Nothing to worry