Cold start ups?

[nissanrcer240]

Every time I start my car up from a cold start, its starts right up but then the rpm's start to drop and if I dont give it some gas it will cut back off. If I hit the gas really hard one time then it will come back down to normal and idle fine and run fine until I cut it off and let it cool down then try to start it again. It just started doing it a couple weeks ago, any ideas what could have went bad or what could be the problem?