As you fall asleep the changes begin. At first your hair starts to melt with individual hairs merging into strands, then into a blob. The surface of the blob turns shiny like mercury or chrome. The bulk of it gradually gathered in the middle, forming a Mohawk shaped silver bar from front to back which helps to hold the hat in place. The area around it looks bald and silver.
Then the changes spread downwards like a thin silvery liquid covering his skin. It covers your ears dissolving the auricles of your ears gradually turning them into truncated cylinders with little vents which could be mistaken for headphones if they weren't directly attached to your head and in the same smooth reflective shine as the skin around them.
As the changes flow further downwards, a pattern emerges. Your face is not covered by the silver and looks just like before, but it is surrounded by a ring where your normal skin seems to abruptly end and turn into a metallic surface. Then your face starts to change, as your jaw becomes more pronounced. What is left of your normal skin turns a shade darker as if you spent months in the sun. The changes also make you look older particularly as you grow a slight stubble.
The wave of your skin turning into a shiny metal surface continues downwards. Some of it seems to split off, creating a ring around your silver neck and turning red and into cloth forming a neckerchief around your neck. Meanwhile the changes continue down your arms, stopping at your right one just above the elbow on your right arm, but continuing all the way down your left arm. Then your shoulders grow in size, seemingly acting as a sort of armour, but making you look more muscular and bulky. This bulk-up continues down your arms even into the parts that were still flesh and blood. If you were awake you'd notice that the silver parts were no longer flesh and blood, but mechanical replacements following your commands swiftly and with high precision.