I drive the same road to work daily in my 06 v8v. I tends to get spirited at times.

Today at about 100mph, the steering would shudder. Normally I would blame a wheel balancing, however....

- the shudder is not a consistent one such as unbalanced wheels, it kind of comes and goes. Little 'bursts', but also in a bit of a consistent pattern - on off on off
- only when going in a straight line, If I turn left or right, it is not present.

No changes to the car, no pot holes hit. Tires are newer (about 3000km on them)

Have you experienced this before?

 

If it was mine I'd put it on the lift and check the tie rod ends (#5 & #6 here, available online as they are used on other vehicles: https://www.scuderiacarparts.com/par.../151/684/24042)... If not them, then try pushing/pulling the top of the tire (while it's in the air) and see if you get movement that would suggest that bushings here: https://www.scuderiacarparts.com/par.../151/685/24050 are worn.

I apologize for showing DB9 diagrams. Yours will be similar.

 

I experienced this similar issue on my 09 Vantage and it was indeed the tie rod ends... it was actually one end and I replaced both of them. It's a Ford part as I recall and inexpensive and easy to replace if you are handy. It doesn't require an Aston specific mechanic but a capable one to make sure you can get thy car lifted correctly.. The tricky part is getting it properly aligned.