Cold Start Knocking 350Z

I am experiencing knocking at cold start up. It only lasts for a few seconds and then goes away. It concerns me and I was wondering if it might be the knock sensor or if it is the lifters going bad. The car is a 04 and it has 80,000 miles on it. Other than the knock the engine runs great. It does use some oil, but not excessive. Any suggestions or advice?