Heat olive oil in a large pot over medium heat. Add diced onions and sauté until translucent.
Stir in minced garlic and sun-dried tomatoes. Cook for another 1-2 minutes.
Pour in chicken broth and bring to a simmer.
Add shredded chicken, heavy cream, Italian seasoning, red pepper flakes, salt, and pepper.
Simmer for 10 minutes, stirring occasionally.
Stir in Parmesan cheese and spinach. Cook until spinach wilts.
Add cooked pasta just before serving or spoon into individual bowls and pour soup over pasta to prevent sogginess.