An alcoholic that I know head shakes and bobs right after he has a few drinks. It seems to be getting worse.

Alcohol is a toxin, specifically a substance known as
ethanol, which is the culprit. The signs you are describing could be indicative of what
is known as Alcohol Related Brain Damage, which is related to the heavy consumption of
alcohol for a minimum of ten years.

Part of this condition
is what is called peripheral neurpothy, or peripheral nerve damage, which results in the
destruction of the nerve pathways especially at the bodies extremities. This leads to
uncontrolled tremours, and in some cases in my own practice, a bobbing head. Another
sign is rapidly moving eyes. DT's are usually found in extreme withdrawal, and costitute
a medical emergency, and this is also called wernickes encephalopathy, which is in
effect an acute reaction to alcohol in the brain. If someone has gone without a drink
for a short time, they are more likely to display sweating and stomach upsets, usually
what is called here in the scotland the "dryBoak" boak being scots for wretching. The
fact that the symptoms you describe get worse suggests  an ARBD style scenario, but it
is difficult to say much more without further symptoms. I would suggest if you haven't
already done so , encourage the person to get to a physician or drug treatment team for
further assessment.

Hope this helps