2008 Holden Commodore Starting issues and rough idle

I have a ve omega which has a problem when I start up first thing in the morning. After about 10 seconds after I turn it on it makes a terrible noise and sounds like it's knocking and running on 2 cylinders but then comes good and wont make the same noise again all day. But then when I start it after that it won't make the noise it just runs really lumpy on start up for around 10 seconds and then come good and will only do it sometimes other times it will start fine like nothing's wrong at all. And it also has a problem starting on a hill when the car is pointing bonnet downwards on the hill it's a very frustrating issue please help