Mountain Biking - speclized rockhopper shifting problem

i just got this bike a day ago used from somone the bike was brand new and this is the first mountain bike i have owned i think somthing need ajusted because when i shift the rear gears thay will shift but then reshift either up or down is there somthing i can do or what need to be done

Most likely you need to adjust, or have a LBS adjust, the rear d cable, most likely a quick adjustment to the barrel will be all you need. If the d hanger is bent, that could cause it as well. If the bike has been sitting for some time clean and oil the chain. If you don't have a lot of experience with that sort of stuff, having a LBS do a quick one over would be money well spent. Most good LBS if you ask will show you how to make the minor adjustments to keep it shifting smoothly.

Although this sounds like a dérailleur adjustment, since it has been sitting a while a few squirts of lube inside the shifters to free up any gumming wouldn't hurt either.

ok guys yea the chain looks dry ill try and lube it up and stuff or take it to the bike shop a little wails away and see what thay say but thanks for the help

My bike did that, it was in the middle of the cassette. I just adjusted the cable and it went away.