97 dodge ram stalling!!!!!?

i have a 97 dodge ram and recently what has been happening is I will start it up it will start perfectly fine then once i put it in drive i noticed the rpm drop very low but then come right back up all this before i even take my foot off the brake then once i start rolling i give it gas and when i let off the rpms drop so low the truck stalls ...it will start right back up and after usually two stalls or so the truck will drive perfect ...it never sputters or anything it always run very smoothly just simply shuts off ..can anyone help me !!!