I've experienced the same thing, many times but not in recent years. Oddly enough, now that I think about it, it apparently stopped happening around the same time I was starting to lose interest in alcohol.
I would usually say tolerance.
Did you feel the rush then get sober or no rush? And was that your first shot of the session?
If you didn't feel the rush I don't know what to say.
If you didn't, the shot either wasn't big enough or its shit gear.
If it was you just need a break, other drugs your on are masking it or your mood and state of mind are masking the effects.
Or your high as shit and have a delusion of sobriety.