Hesitating

I own a 1998 Chevrolet Lumina with 140,000 miles on it. I just started having a problem (my first ever and I have had the car since 1998). It is starting to hesitate when I start to accelerate. Actually, I am not sure if hesitate is the correct term. It starts to jerk. It does this four or five times in a row and then quits. It doesn't do it everytime I accelerate but it is persistently getting worse. I keep up the maintenance on it myself. I change the oil, oil filter, and air filter every 3,000 miles and I perform other maintenance as suggested by the manuel. But this has me stumped. Could it be my spark plugs and plug wiress or should I look for something else? :