Drunk after one drink, deep sleeper, sometimes hyper?

This is about someone I know well who has an odd set of symptoms (I swear it's not me!). I know he needs to see a doctor but I'm wondering if anyone could shed any light on this in the meantime...

He's a big guy (over 6' and over 200lbs but not really fat) 60 years old, is an avid bike rider (rides sometimes 10, 20 miles per day), eats a huge amount of healthy food and vitamins (but all that exercise keeps his weight off), and his body is in good shape of course.

But here are the symptoms:

- If he has even one glass of wine, he gets seemingly drunk, unsteady on his feet, etc.

- He sometimes trips and falls; it's happened 3-4 times in the past year.

- He often falls asleep watching TV, etc. and can be hard to wake up (dog barking right in his face and he just keeps snoring - and his hearing is OK).

- He often has mood swings, sometimes gets really hyper and won't shut up, talking until 3-4AM.

Any ideas?