So after I've had my car running& turn it off to go into a store for instance when I turn it back on before the engine starts it makes this kind of banging sound, and then the engine starts BUT ONLY sometimes. It doesn't do it every time& once it's running it normal. And if the car has sat over night or whatever for a decent amount of time, no weird sound. Only does it sometimes when I start it up off of sitting for a short period of time. Any idea?