Check the set screw in your trigger. A long time ago I had issue with that screw getting loose and actually over-tightening itself which puts pressure on the sear. This caused some doubles and burst fire. If you pull the trigger to the rear and work the hammer it should feel smooth and you should feel no pressure of any parts engaging or catching. If yours does that the over-travel screw is too tight and causing your issues. I ended up taking that screw out in a couple of my guns as, even with loctite, it would eventually work itself out and the benefit was less than negligible. If you rule out this I would replace the sear spring as posted above and inspect the hammer hooks. Not sure what your round count is, but have heard some shooters wearing out the hammer hooks and the gun doing some goofy stuff.