What causes clattering or clicking sound when you start it up early in the morning on a 1993 lincoln mark viii?

Sounds like lack of lubrication on the camshaft, especially if the sound goes away after 10 sec. or so.
If you are on a cold climate, shift to a lighter oil weight, such as 5W-30. Other option is to use commonly available oil superlubricants/ additives. Origin of problem is that oil gets drained down during the night, camshaft gets dried up, and on first start in the morning, oil pump works hard to pump the heavy oil to the top of the engine. On hotter climates, some oil stays attached to the camshaft and valve lifters.