Hey stumars
the exact thing happens to me. My pulse is normally around 55 and the night after I have a drink or 2, my pulse is around 80 upon awakening. Even if I don't any sugar and have a sugar free drink (the mixer being sugar free), it still happens. Unless you have a pre-existing heart condition, it's not life threatening but I agree with stan, avoid alcohol for a while.
If you "must" have a drink or 2, I have found that what can reduce the palpitations (but not eliminate them) is to eat alot of fat and protein and no carbs while drinking.