tiny bubbles in my Cab -What are they?

I have a 15 gal carboy with cab in it that feels the tiniest bit fizzy on the tongue. I made the wine from grapes, not a kit, and put it in the carboy around the end of october. I tasted it a few weeks after and it was great. Another few weeks went by, and I racked it. Just before and after racking and even now, another 3 weeks later, it has the slightest fiz on the tongue. I was thinking that it may have been ML hapenning, but I have 5 other containers that do not have this problem. I treated them all in the same manner. I have thus far been patient, and done nothing, hoping it will stop, but I have also thought that it needs to be degassed. Any thoughts?