?Rattling? noise when car is cold and driving

Hey everyone, I got my koup sx 2 weeks ago and have about 600 miles on it and I'm getting a rattling type noise when my engine is cold and i drive the car. It mainly happens going from 1st to 2nd gear and then into 3rd. It goes away when the car is warmed up tho. Anyone know what this might be/ have this problem? I made an appointment with Kia but it wont be for a few days and I kinda wanta know if its okay to drive for the next few days with it. I'm thinking it has something to do with the clutch but irdk. Any help would be greatly appreciated!!