Centry key lite

my Grand Cherokee acts like it's hesitating cutting out and it actually will die on me while driving it'll cut out and then like it's going to cough cough and then RPMs go up and down and then it dies sometimes when I start it up it starts up and then goes right off a lot of times it will stay on and I drive it and drive it and then it will start cutting out you'll hear it goes into gear it's already in there but it sounds like it's going into gear and then you watch the RPMs and it will not go down I have to keep it revved up and usually it'll die on me I pull over and I restarted it and sometimes it will start back up and stay started and sometimes it will start up and die I have three keys to it and it's got a light on the dashboard saying it's the century key I can't believe I have 3 keys and only and one of them work all the time I've only had the car since last June but I've had this problem since then do I need to get a new key programmed what do I do I'm afraid if I do and spend that kind of money on it that it won't be the problem but the engine light does not come on,,,I've went through three mechanics and it's been in the shop 3 times overnight it won't act up on the mechanics only me I don't understand I'm not illiterate to cars I am a female but I've raised around mechanics and been married to two of them help me