You mean that by the time you bring it in, the engine is warm and not making any noise?
If the tapping noise is very light, and goes away as soon as the engine warms up, I wouldn't worry about it. If the tapping persists after the engine is warm, you might have to get a valve lifter replacement, by swapping out stock lifter or lifters for ones that "take up the slack" so to speak. This is fairly involved and requires removal of the camshaft on either the 4 or the 6.
It really depends how a) how loud it is and b) if it goes away quickly or not.
You might also try switching to a synthetic oil, which may help get lubrication to the upper engine faster, when the engine oil is cold.