My 1999 olds 88 is running very ruff and sometime cut off this problem started last night , i haven't done anything so for to the car to fix the problem

Could be several things. The first thing I would check is the spart ignition. One way to check to see if you are getting proper spart is to take one spark plug wire off, insert a philips screw driver in the spark plug wire end and hold it about a quarter inch from any metal part of the engine. Have someone turn the engine over and watch for a spark from the screwdriver to the engine. Don't touch the metal part of the screw driver, the spark will pop you pretty good. There shoud be a big sharp spark, if not you may have a bad coil in the ignitions system.