Almost certainly the ignition module (small black box mounted on top of the left hand inlet manifold at rear). Pouring cold water on it can help revive it a bit quicker but they also often just fail completely. The module inside can be replaced separately (actually a GM part). Kirby Palm’s book has a big section on it. I’ve done two in my car over 10 years, last time was about 6 years ago but the one before that only lasted about 18 months. I carry a spare box in the car for that reason.