Sudden loss of speed for no reason. was traveling at 35 mph when vehicle suddenly dropped to 22 mph. Stepped on gas with no response. I know the 22 mph because it showed up on warning illuminator. Car behind me almost hit me because he had no indication (prior warning). Turned off at closest exit, turned vehicle off then on restart things were normal. Took to dealer and they found nothing in computer code or mechanical to explain why this happened. Am an older women afraid what will happen if repeats on highway going 70+ mph. Please made Hyundia find and fix.