Q: my 2008 jeep shakes sometimes when I start it up, does it periodically

If you are referring to the first few minutes of driving when the engine is cold, the engine coolant temperature sensor must be working properly to signal the PCM to enrich the mixture on cold start. If there is a fault with that sensor, you can experience rough idle as you are describing. Other possibilities are uneven cylinder compression, a vacuum leak, an air induction fault like a stuck idle air control valve or a faulty throttle position sensor, problems with the mass air flow sensor, defective spark plugs, a weak coil and defective oxygen sensor(s). If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a rough idle diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.