“And at the beginning of a sentence? During the 19th century, some schoolteachers took against the practice of beginning a sentence with a word like but or and, presumably because they noticed the way young children often overused them in their writing. But instead of gently weaning the children away from overuse, they banned the usage altogether! Generations of children were taught they should ‘never’ begin a sentence with a conjunction. Some still are.
“There was never any authority behind this condemnation. It isn’t one of the rules laid down by the first prescriptive grammarians. Indeed, one of those grammarians, Bishop Lowth, uses dozens of examples of sentences beginning with and. And in the 20th century, Henry Fowler, in his famous Dictionary of Modern English Usage, went so far as to call it a ‘superstition.’ He was right. There are sentences starting with And that date back to Anglo-Saxon times.”
— David Crystal, The Story of English in 100 Words. St. Martin’s Press, 2012.