A bit of a leak in the head gasket may slowly allow coolant into a combustion chamber overnight. Try this:

Before first morning start -

Open hood and remove coolant filler cap. Set it aside securely, leave hood up.

Get in and position yourself to where you can see the coolant filler opening. Start the engine and watch. See if the coolant in the overflow tank wells up and overflows out the opening.

A small head gasket problem will allow combustion pressure into the cooling system until the engine heats up. Thus the coolant overflow only with a cold engine. BTDT

If you don't see that, hooray for the head gasket, but you do have some other problem causing the smoke. Leaky injector making one cylinder very rich at startup?

Good Luck,

Bob

:>)