In a large bowl, stir together shrimp, cumin, lime juice, cilantro, garlic, and 2 tablespoons oil and season with salt and pepper. Toss until combined, then let marinate in the fridge 10 minutes.
In a large skillet over medium heat, heat remaining tablespoon oil. Add shrimp and marinade cook until pink, 2 minutes per side.
Assemble wraps: Add shrimp and avocado to lettuce, drizzle with sour cream, and garnish with cilantro.