Engine has this cold start rattle that occurs only on the first start of the day. What the issue is, is the timing chain tensioner is a little gunked up from oil varnish, as a result the tensioner does not extend all the way and causes that awful rattling noise. The recommendation was the replace the tensioner, which is not an expensive part, but it is incredibly inaccessible and must be performed by a skilled mechanic. While you are over there, you might as well cover the rest of the timing chain system with a kit.

You might get lucky and be able to perform an engine flush to get rid of some of the varnish. But it would also be recommended that you change your oil over to 5W30.