Steering column shakes during braking/bumps!!

(2006X S; 75K) So I've got this steering column shake/vibration issue that's becoming more prevalent the last few weeks. The shake only happens while driving over normal bumps in the road or under heavy braking; other than that it never happens and the steering is otherwise smooth and accurate. There is no play in the steering wheel and the shake definitely comes from down in the column. I can feel it in the wheel and it makes a noticeable sound. No foreign objects in the housing (pennies, Legos, etc.) Why bumps and/or braking? Appreciate any ideas!!