Preheat oven to 350°F. Toast pecans for 6-8 minutes, then cool and set aside 1/4 cup for garnish.
Prepare spice cake according to package, bake, cool, and cut into 1-inch cubes.
Mix cream cheese, pumpkin, powdered sugar, pumpkin pie spice, and vanilla until smooth. Fold in whipped topping.
Layer 1/3 cake cubes in a trifle bowl, drizzle with caramel, sprinkle with pecans, then add half of pumpkin filling. Repeat layers and top with whipped topping and garnishes. Chill for at least 4 hours.
Notes
Chill thoroughly before serving. For homemade whipped cream, whip 3 cups heavy cream with 1/3 cup sugar and 1 tsp vanilla until stiff peaks form.