Front-end shake

[NorthIdahoTexan]

Experienced a one-off braking issue while descending a 7% grade. Had driven ~100 miles, stopping as needed with no issues. Began descending about 3 miles of maximum 7% grade touching the brakes infrequently as my 2018 Silverado 2500HD Duramax does a great job of reducing speed when off the petal. No towing selector, downshifting, no engine brake engaged. I’m just about to level ground, slowly apply my brakes and HELLO! Front-end/wheels start shaking like I’m about to throw a wheel. I feather braked to a stop on a side street, checked for play in the wheels and nothing evident. Continued another 120 miles, up hill/down hill, two 9% grades and only one instance of a very light wobble.

Suggestions/similar situations?