1995 Buick Regal surges, idles high

Engine surges upon starting and idles high, can see rpm's fluctuate when driving also. Upon coming to a stop the engine has stalled. At other times it will run 10 miles with no issues. When the surging starts the "Check Engine Light" will come on, but upon restarting the engine it may run fine and no "Check Engine" light will come on. This can occur when the engine is cold or hot.