sometimes runs good

my 97 olds 88 started having a problem after shutting it off it would not restart till it sat for awhile maybe an hour so i would drive and not shut it off till i got home ..was driving it and it shut down completely on the road went back later and it start right up ...fuel pump is good ...now some times it wants to run fine and other times it acts like it is missing or running rough??

could this be electrical or a sensor...ignition control modual?