Heat the olive oil in a large pot or deep skillet over medium heat.
Add the chopped onion and cook, stirring occasionally, until translucent, about 3-4 minutes.
Add the minced garlic and cook for 1 minute until fragrant, stirring frequently to prevent burning.
Pour in the chicken broth and diced tomatoes with their juice. Stir in the dried Italian seasoning, red pepper flakes, salt, and black pepper.
Add the linguine pasta to the pot, pressing it down gently to submerge it in the liquid. Bring the mixture to a boil.
Reduce heat to medium-low and simmer uncovered, stirring occasionally to prevent the pasta from sticking, for about 10 minutes or until the pasta is almost al dente.
Add the shrimp and fresh spinach to the pot. Stir gently and cook for an additional 5 minutes, or until the shrimp turn pink and are cooked through and the spinach has wilted.
Taste and adjust seasoning with additional salt and pepper if needed.
Remove the pot from heat. Sprinkle freshly chopped parsley and grated Parmesan cheese over the pasta. Stir gently to combine.
Serve hot, garnished with extra Parmesan if desired.