Oil Overflow when cold.

I've had my coupe for five years and this has happened a few times. While cold I do an inspection of the engine area. When I remove the oil cap the oil is right up to the top as if it is overfull. If I start the engine and let it warm up and then shut it down then re-check the oil, it is at the proper height on the oil stick - CRAZY! I've never seen this. Any ideas? Larry Mccartin Grants, New Mexico if you would like to talk (520) 444-4390 Happy Flying.