Early for me..........

[micmak]

But, can you start a sentence with but, I think not. Today has been a really boring day on AB. Better tomorrow (I hope) Goodnight people.

[Quizmonster]

"The widespread belief that 'but' should not be used at the beginning of a sentence seems to be unshakeable. Yet it has no foundation..." (I won't bother going any further.)
That is from Fowler's Modern English Usage, generally recognised as authoritative in such matters. So, yes, you CAN start a sentence with 'but' and you'll find evidence of that in the Bible and in multitudes of other circumstances involving good-quality authors.