Just got a 97 bravada a few days ago and it was doing something similar. Just changed all the plugs and wires and it purrs like a kitten now. Looked like some one only did 5/6 plugs last time. Middle one on drivers side is a pain in the ass to even get the socket onto. I'll see if that fixs the cold start problem tomorrow. My sisters car had the only starts in neutral thing a while back. Neutral position sensor/switch was the problem and fix.