Occasional = sometimes, not very often. It means "I sometimes drink wine". People say that to mean "I don't drink very often, and when I drink, I don't drink a lot". But it's sometimes used as a joke - I say things like "I enjoy the occasional half a shandy" , when I actually get very drunk on a regular basis.

It means that the person enjoys having a glass of wine every now and then, meaning that it's a rare occurrence. With regards to your second sentence: "I occasionally enjoy some glasses of wine" - you would not say "some glasses" - the correct way to rephrase this would be "I occasionally enjoy a glass of wine" which is the same as "I enjoy the occasional glass of wine". Hope this helps!