2011 WRX intermittent Steering Wheel Shaking

[11WRX707]

Hi I'm looking for some advice. The car is a 2011 WRX, iv owned it for about 2 months now the previous owner replaced the brake booster, brake master cylinder and all 4 calipers, I have replaced the rear brake lines because they were rusted out and had a pretty big leak and the front brake hoses for a small leak.

Occasionally when driving on the highway my car will develop a small shake in the steering wheel that gradually gets worse to the point where it feels like the whole car is shaking, it stops once I pull over. If I wait a few minutes then start driving again the problem will sometimes disappears other times when I go to drive again after pulling over it feels like something is trying to stop the car from moving almost like I'm trying to drive with the parking brake on and the shaking will continue.

I took it to a local shop and they couldn't find anything wrong with the brakes or any of the suspension components and unfortunately the weather has been bad lately so I haven't been able to crawl under the car to check things out myself. This is my first subaru and i dont have much experience working on them, I would really appreciate any ideas or suggestions on what to check
or do next