Heat oil in a large skillet over medium-high. Add onion, jalapeno, and garlic; season with salt and pepper. Cook, stirring occasionally, until onions are softened, 4 to 5 minutes.
Add tomatoes and corn; cook, stirring occasionally, until corn is heated through and tomatoes are soft, 4 to 5 minutes.
Add shrimp and cook, stirring occasionally, until opaque throughout, 2 to 3 minutes. Serve immediately with tortillas, cabbage, salsa, sour cream, and lime wedges.
To thaw frozen shrimp at the last minute, place in a sealed plastic bag in a bowl of room-temperature water. (Change water once or twice, as it becomes cold.) Shrimp will be ready to use in about 10 minutes.