I own a Nissan 300ZX Turbo 86 yr. Only 127K on it-AT. It’s in great condition for a 21 yr old car. I’ve noticed this more frequently that the car shudders or hiccups when idiling and or going slowly. Is this a sign of that it needs new spark plugs or what? I had it taken into AAA for the 100pt. inspection, but they didn’t notice that was happening. Any ideas before taking it in?