No, it is not recommended to start baking bread before preheating the oven. Preheating the oven is an essential step in bread baking because it ensures that the oven reaches the desired temperature before you put the dough inside.
Bread dough needs a consistent and controlled temperature to rise properly and develop the desired texture and flavor. If you put the dough into a cold oven and then start heating it, the dough will be exposed to temperature fluctuations, which can negatively affect the bread's rise and structure.
Preheating the oven allows the dough to begin baking at the correct temperature right from the start. This helps create a good oven spring, where the dough rapidly rises and expands in the hot oven environment. It also contributes to the formation of a desirable crust on the bread.
To achieve the best results, it's important to follow the instructions in your bread recipe, which typically include preheating the oven to a specific temperature before baking.