intermittent front brake grinding sound, stops after applying brakes sometimes

Sometimes brake grinding sounds can come from the mating surfaces of the brake pads and brake rotors not being burnished properly, such as with brake rotors that have hot spots or brake pads that are moving too much in the calipers. Get some assistance to have a closer look at the pads and rotors - I think you'll find there are actually issues there; also the grade of brake pads used may be "safe" but not noise free.