Hey, so my mercedes seams to tremble when I start it up like it is on the verge of dying at very low revs. When I put it into reverse it makes the whole car shake. Also, when I'm driving, it will start to bog when I press the gas so I have to keep my foot light on the gas. Then sometimes it will die while I'm driving. I think it has something to do with fuel not getting to the engine so maybe the fuel pump is out. But it doesn't always do this... sometimes it runs fine. Can anyone help?