Preheat your oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat. Add the shrimp, garlic powder, cumin, chili powder, salt, and pepper. Cook until the shrimp are pink and opaque, about 3-4 minutes. Remove from heat.
In a separate bowl, mix together the sour cream, heavy cream, and half of the green enchilada sauce.
To assemble the enchiladas, place a few shrimp in the center of each tortilla, sprinkle with a bit of Monterey Jack cheese, and roll them up tightly.
Spread a thin layer of the remaining enchilada sauce on the bottom of a baking dish. Place the rolled enchiladas seam-side down in the dish.
Pour the cream mixture over the enchiladas, then sprinkle the remaining cheese on top.
Bake in the preheated oven for 20-25 minutes, or until the cheese is bubbly and golden.
Garnish with chopped cilantro if desired, and serve hot.