Preheat oven to 350 degrees and spray both cake pans generously with cooking spray.
Wash and dry strawberries, raspberries and blueberries, then place into separate bowls. Place whipped cream into a large bowl and set aside.
Place cake mix, eggs, milk, oil, sour cream and vanilla pudding mix into a large mixing bowl. Stir slowly to combine, then stir vigorously until batter is well combined. Transfer evenly to prepared cake pans and bake for 25-30 minutes, or until baked through. Remove and let cool completely.
Flip cakes over onto parchment paper and cut into 1/2 inch cubes.
Place a layer of cake cubes into trifle bowl, then top with a thick layer of whipped cream. Arrange a layer of strawberries, blueberries and raspberries over cream. Repeat another layer of cake, whipped cream and berries filling to the top of your trifle bowl.
Place trifle into refrigerator to chill until ready to serve.