He mentioned 5w40 Grade oil. That's not that thick, or is it? A neighbour's car gave the same problem, he got the tappets done and it became fine. That's why I think its the tappets because on a cold startup, they usually need more "play" which isn't possible due to tightening up, and hence the noise and poor shuddering behavior in some cases.
May be I am wrong but I can't come up with another theory, may be an engine expert can guide us better.