Lights jump/flicker

GMC Suburban 96 / 140,000 miles With the lights turned on and the engine idling, the interior lights and headlights will flicker/jump. I have not added any aftermarket equipment. The battery needle will jump with the flicker/jump. My alternator and battery is fairly new (both replaced within 6 months). The engine runs smooth, no power window problems or any other electrical problems. Any help?