1999 Toyota Camry Toyota Camry 4cl making noises

During the morning when im warming my car up at around 2000rpms my car starts to make these rattling noises. Once my car is warmed up at about 1000rpms or 900rpms it sounds fine but if I gas it back up to 2000rpms it makes this same rattling noise again. My car sounds perfectly fine at 2100rpm or 1900rpm but during any time that I take it to only 2000rpms its making this rattling noise. Also the car could be warmed up and if its at 2000rpm it'll make this rattling noise again. So pretty much anytime its at 2000rpms it makes this sound. Im just hoping someone might know what this means?