In a bowl, season shrimp with 1/2 teaspoon of red pepper flakes and salt and pepper to taste. Set aside.
In a pot over medium heat, bring about 4 quarts of salted water to a boil. Add linguine and cook for about 1 to 2 minutes shy of package directions. Drain well, reserving 1 cup of the pasta water.
In a wide pan over medium heat, heat 1 tablespoon of the olive oil. Add shrimp and cook for about 1 to 2 minutes on each side or just until color changes. Remove from pan and keep warm.
In the pan, add the remaining 4 tablespoons olive oil. Add onions and cook until softened.
Add garlic and cook for about 30 to 40 seconds or until aromatic.
Add the remaining 2 teaspoons red pepper flakes and cook, stirring regularly, for about 20 to 30 seconds.
Add crushed tomatoes and wine and bring to a boil. Lower heat and simmer for about 15 to 20 minutes or until reduced.
Add pasta, shrimps, and reserved pasta water. Gently toss to combine and evenly coat with sauce. Continue to cook for about 2 to 3 minutes or until pasta is heated through and al dente.
Season with salt to taste. Divide into serving plates and garnish with Parmesan cheese, if desired. Serve hot.