There is nothing wrong with starting sentences with “and,” “but,” or other similar conjunctions. You may, however, encounter people who mistakenly believe that starting a sentence with a conjunction is an error, so consider your audience when deciding to structure your sentences this way.
Consider the example below:
Separating these sentences with a period is a dramatic way to emphasize the contrast introduced by but. Not everyone, likes this style, though. It’s also possible to connect these sentences with a comma:
Some readers especially dislike seeing the conjunctions or, nor, and yet at the beginning of a sentence. While it may not be an error, starting sentences with these words does sometimes seem melodramatic.
Consider the examples below: