Cook the fettuccine according to package instructions until al dente; drain and set aside.
In a large skillet, heat olive oil over medium-high heat. Season chicken breasts with salt and pepper and add to the skillet.
In the same skillet, add minced garlic and sauté for 30 seconds until fragrant.
Add chopped sun-dried tomatoes and Italian seasoning to the skillet; cook for 2 minutes.
Pour in heavy cream, stirring to combine, then bring to a gentle simmer.
Stir in the grated Parmesan cheese and the spinach, cooking until the spinach wilts.
Slice the rested chicken and add it back to the skillet along with the pasta; mix to coat everything well.
If the sauce is too thick, add reserved pasta water gradually until desired consistency is reached; taste and adjust seasoning.
