The key to keeping your baked spaghetti nice and saucy is to follow the ratio of pasta to sauce and also to not over-bake it! When reheating in the oven, I suggest covering with foil so it doesn't ...
To make the alfredo spaghetti ... generously with the grated mozzarella and bake for 20–25 minutes until golden and bubbling. Remove from the oven and allow to sit for 5 minutes before serving ...
Let it all come up to a gentle simmer, then transfer the whole lot to the warmed dish, stir it once and then bake, without covering, on the centre shelf of the oven and set a timer for 20 minutes.