2000 Dodge Ram Knock/clunk when cold

My 2000 dodge ram 5.2 is making a knocking noise when I first start it up in the morning. It'll only do it when it's cold outside. It is also dry starting. The clunking sounds like something is hitting my driver side valve cover. It'll do it for about the first 5 minutes after I start it up. I've noticed if I wait until the afternoon it won't do it. But when it's real cold in the morning it does it. It dry starts every time I start it up if its been sitting for more than 30 minutes. There's plenty of oil and its the correct weight. Puralator oil filter with anti drain back. New sending unit. Any other ideas? I'm thinking its a oil pump but don't wanna put one on unless I know that's it.