sounds like your disconnector isn't moving freely....either that, or your sear spring needs to be replaced.
try giving the frame guts a thorough cleaning, re-lube and test fire. If it's still doing it, replace the spring.
I had this happen on my Les Baer and again on my SA. (LB was a worn out sear spring, the SA was a rough disconnector that needed to be polished some)
eta: just thought of something--dry fire it, and hold the trigger back. Cycle the slide, then release the trigger. Did you hear a click? You should hear it when the trigger moves forward a tiny bit. If you don't hear it and your pistol has an adjustable trigger, backing the set screw out a quarter turn should fix it.