2005 Jeep Liberty Renegade 3 7l V 6 Engine Oil Light Comes On Only Start

i have a 2005 jeep liberty renegade (3.7L V-6 ENGINE)! my oil light comes on when i only start it in the morning! after i start it the engine it makes a ruff sound! so i have to restart it to make the oil light go out an to make the engine run smooth! it only dose it after it sit over night! just that one time only on the first start up! what is the problem!