Congress may not be formally consulted before the President decides to use air strikes; he seems to be generally contemptuous of decisions with which he does not agree and finds ways to circumvent them. The War Powers Act has been ignored and resisted by other presidents who believe it to usurp their constitutional powers to act as the nation's Commander-in-Chief.

Popular opinion, at this time, is against military intervention in Syria so I don't think Members of Congress want to be on the record of having voted for intervention even though a number of them may think it's necessary. Anything this controversial is likely to threaten their reelection prospects in competitive districts and those with presidential ambitions may may be particularly squeamish about being on the record.