Car stalls on startup

Hey guys haven't been around for a while, but I am back with a minor problem I need some help on. Last couple of days when I crank the car it revs up like always, but then the RPM's drop really quickly instead of coming down slowly like they always have. They drop very quickly to between 300-400 RPM's then jump back up to about 600 and then it idles normally. A couple of times they have dropped so quickly that the car has died. Normaly my tach jumps to about 2K when it is cranked then slowly settles to about 600 RPM's. I haven't pulled the codes yet, planning to do that my first day off. Just wondering if anyone has any suggestions on what to check. I was thinking the IAC, but it idles fine after start up.

Yeah guys my first step is gonna be cleaning the IAC and intake with throttle body cleaner. It has been about 8 months since I cleaned the IAC. I haven't driven the car anywhere but back and forth to work the last few weeks which is about a mile and a half from my house. I probably haven't had it over 35 miles an hour in 3 weeks. Last night I took for a pretty good drive down some back roads and on the interstate. It cranked and idled normally this morning.