Wild MPG instant reading

Was in heavy traffic for about 1 hour on I 5 goin south through Tacoma WA today for about 10 to15 miles or so and the reading would go from 0 standing still to 99 As I crawled along one or two mph, then down too 25, up down and even when I got out of the slow traffic it was still bounceing up and down. When I got too my destination I cleared all the readings and it would still do it as I moved the truck to park it. It run good other wise and drove fine, it started right up three or four times after I had it parked. This is a 360 mile trip over and the same going back so hope it runs fine when we head back Saturday. Do you think I should see if I have it checked Friday before I head back to Eastern Washington