The engine is surging

I've got the same problem! The engine is surging. I mowed almost the entire lawn. After about 1 -1/2 hours, it started surging. Quit several times. I finally put it away to avoid having to push it to the garage. I have a NEW SW 5000 (as of June). I've mowed maybe 3 times with it, so I'm not sure what to look at...Everything is new. Does anyone have experience with TORO warranty work.