Bring a large pot of salted water to a boil and cook the linguine according to package directions until al dente. Drain and reserve.
In a large skillet over medium heat, warm the olive oil and 2 tablespoons of the butter until melted.
Add the minced garlic and red pepper flakes to the skillet and cook, stirring, until fragrant, about 30 seconds to 1 minute.
Add the shrimp, season with salt and pepper, and cook until the shrimp turn pink and opaque, about 2–4 minutes depending on size.
Stir in the Italian seasoning and the baby spinach and cook until the spinach is wilted, about 1–2 minutes.
Add the cooked pasta back to the pot or into the skillet with the remaining butter, then add the Parmesan and chopped parsley; toss until the butter is melted and the pasta is evenly coated.
Stir in the lemon juice, adjust seasoning if needed, toss to combine, and serve immediately.