Bring a large pot of water to a boil and cook pasta according to package directions.
During the last 5 minutes of cooking the pasta, heat 3 tablespoons of butter in a large skillet over medium heat. Once melted, add the shrimp, garlic, red pepper, paprika, salt, and pepper.
Cook the shrimp, stirring often, for 3-4 minutes or until pink on the outside.
Remove shrimp to a plate and set aside.
Add the remaining 5 tablespoons of butter to the skillet and melt over low heat.
Use tongs to remove the cooked spaghetti from the pot of water, allowing most of the water to drip off the spaghetti, and place spaghetti in the skillet.
Add the spinach and Parmesan to the spaghetti and toss to coat, continuing to cook over low heat stirring constantly, until the spinach has wilted.
Return the shrimp to the skillet and stir to combine.
Sprinkle with parsley before serving. Serve with additional Parmesan, if desired.