I have this exact same issue with my 17 Pacifica. I use it as a long distance courier delivery vehicle and this started happening to me last night with 299,505 on the odometer. I had my normal mechanic scan it as well as my transmission specialist and neither could pull up anything as the code only lasted a few minutes afterward, however, I noticed that when I lifted my foot off the gas even driving on level ground, the van would jerk a little bit. I am also do for my 60000 mile trans flush. So possibly a transmission issue. I will know within a week or two and another five thousand miles, lol!
As an aside, I started experiencing hard shifting at 187,000 miles. Original transmission is still somehow working over 100,000 miles later. So anyone experiencing this should just power through, keep flushing fluids regularly and accelerating at a medium to brisk Pace usually stops the hard shifts. I have a trans from a used 19 Pacifica waiting at the shop for when this one goes. Cost 3200 and only had three thousand miles on it when the vehicle was wrecked. Labor will be 1100.