2005 Hyundai Tucson V6 stalling?

About 2 weeks ago the car just shut off in the McD drive through after about 30 mins of highway driving. Tonight on highway it almost felt like it would stall while going 60 mph. Two mins later in traffic back up when I was down to just cruising with foot on/off brake it died again. Once put in park it has started right up again both times. Temp is ok, no check engine light coming on. Any idea what may be causing this? If not, is it something the dealer should easily detect if hooked up to diagnostic equip?