1993 Jeep GCL running very rough, but not always

I have a 1993 Jeep Grand Cherokee Laredo with 183,000 miles and the 5.2L motor. Sometimes when I start it, it feels like the motor is missing, possibly not running on all cylinders. Other times it starts up perfectly and will run great for awhile, then it experiences a lack of power, cuts out and lopes on idle, down to 500 rpm on tach. The other day, it started great, ran great into town, then started missing, loss of power, etc. Got so bad when I accelerated, the steering wheel was shaking badly. Limped home. Parked it. Today, it starts fine, went around the block, no problems, runs normal, engine sounds and feels good and normal exceleration ! I am afraid to drive it right now because I don't know when or where it will start doing it again! I have only owned it for a month, but it came with excellent maintenance records. I tried the on/off/on/off/on watch engine light and count how many times it flashes for code number, but it only flashes 5 times and then 5 more times. What does that mean, code 10? Well, the codes I downloaded start at 11. Any help you can give will be appreciated and I am giving a donation! Great service! Thanks, Vance.