2014 Cadillac ATS - Mystery noise

when starting my car its this loud annoying humming noise?sound that goes away …about 30 Seconds or so it goes away…sometimes while driving it happens as well

Could be the smog pump. California ATS have an electric smog pump.

Do these still have air shocks with a pump? If so, it could be a leak in the air shock system and pump is turning on to compensate