My engine starts to putter after running for awhile?

Hi, i have a 98 oldsmobile 88 LS and ive noticed that after driving for awhile and then stopping and shutting off the engine and then getting back in to drive again shortly after the engine seems like it wants to die for awhile, it will kind of putter, and then it will start driving smoothly again after a few minutes or so. Can anyone tell me what the problem might be. Thanks alot.