Sometimes. BUT it depends on the sentence you had in mind. Very rarely the sentence works with but as the starting word.
The race commences when the starting pistol is fired.
I was also confused about this. This link really helps: http://grammar.quickanddirtytips.com/starting-a-sentence-with-however.aspx
Being able is the correct version of the sentence. You can use it as a fragment of any sentence.
To me, the Canyon was a stunning place.
'anxious' she said after being asked how she felt.
No. You should say: "You were starting to do your homework when he came in."You rarely have two conjugated verbs in a sentence unless it is compound or there is a dependent clause in the sentence.
The student was starting to aggravate the teacher with the constant questioning and commenting on the material being covered.
It is interrogative, being a question and starting with the word "who".
No, a comma is not needed after "yes" when starting a sentence.
conditional sentence
starting a sentence with "at which time?
sentence is the collection of words.
I'm
The sentence is:"You are starting to sound CHAOTIC."
A sentence starting with had would be a question: Had you seen her before that?
That depends on if the word is being used as a noun or a verb. Noun: That window has a crack in it. Verb: That window is starting to crack.