How many chicks do you have besides this one? Few days old chicks usually are "lethargic" as they sleep a lot. The bobbing head though is odd, especially if it's just this one. Is it eating and drinking?
If I see a chick that's acting odd, and I'm sure it's just that one, and not coccidiosis, I give them all vitamin water for one day, probiotic water the next, bottled water the next, and repeat for a week or two.
For vitamins, I use Nutri Drench or Poultry Cell
For probiotics, for baby chicks, I use Hydro Hen, for older ones, they get that or Egyptian yogurt.