Joe Nation wrote:
it is always better to avoid beginning a sentence with a preposition
I must correct myself: there is no old myth being peddled here, just an error caused by confusion. There is an old grammar prescription that one should never end
a sentence with a preposition, but nowadays most language experts don't abide by this "rule"—it's often called a myth. On the other hand, I've never, ever, heard of a rule forbidding the practice of starting
a sentence with one.
On the other hand, Joe likes cars.
After church, we visited the zoo.
By noon, the meeting should be finished.
Over the summer break, Peter read six novels.
After an hour, they decided to go home.
Under the table, the dog found some food.
In the middle of the night, the baby woke up.
In the desert, it is very hot.
There is a fairly widely accepted recommendation that one should use a comma following an introductory prepositional phrase, especially if it is longer than four or five words.