Greg,
I wonder if it is the Comtan. I take a similar mixture of sinemet and entacapone and find that, especially if I am not being physically active, i get sleepiness, just as you describe, in the morning.

My pharmacy has recently started adding a 'may cause drowsiness' message to entacapone.

On the other hand just the right incline of my head can do the same thing!

Lindy