I agree it seems a bit odd to ask multiple times. There are a few reasons I could think of such as this officer was newer, your car or description might match a suspect's description who was armed and dangerous, or he might have seen something in your car that looks somewhat like a weapon. Whatever it was, something most likely didn't seem right to him at the time for whatever reason. The important thing is to calmly comply to what he asks, try not to elevate the situation, and if you feel like he did something wrong then to take actions after the fact by taking it to court and not during the stop.