Engine continuously surging on cold start up

[Equitas]

When I start my car cold, I find that the engine revs up (higher than a normal warm idle -- perfectly normal) but then drops down to a normal low idle (perfectly acceptable) BUT THEN CYCLES and does it again, and again, and again....each time the cycle shortens until it is reving at the normal warm engine idle speed. It doesn't sound normal.

What does this indicate? Sounds like there is a problem with my cold idle thingy. Is it the thingy, and if so, what is the thingy called and what should I do about it?