For awhile now my work truck, 2006 F-150 with 5.4l engine, 108,000 miles will crank with a slight miss, possibly a ping while cranking. I will sometimes have to crank it twice to get it started if it fails to start the first time.

Once started it runs great, no pings, no misses, just runs good, mileage is the same as it always has been. Plugs where changed about 20,000 miles ago.

Any thoughts on what it could be?

Thanks