Acceleration

After stopping, when accelerating, 2005 hyundai tucson****** forward several times as if it doesn't want to go, then goes smoothly, it is due for tune-up, at about 58,500 miles, had problem before with smoke/they said it was mist from vents, they checked it about 6 times, nothing, they then found something else, have had regular tune-ups, oil changes, dealer said due for big tune-up $399+$199 for certain spark plugs since it's a v-6, plus tax, said it could be more if something else is wrong when they look at it, are tune-ups this much now? Was ready to trade in, but can't while it's doing this, hate to dump this kind of money if I'm not going to keep it. Any help?