Issues with steering wheel shaking
 

I have a 2012 4Runner SR5 I bought brand new with 47 miles on it. After driving it for around a year I noticed a slight shaking in the steering wheel that gradually got worse. I’ve taken it to multiple shops, including the Toyota Service Center, Firestone, Costco Tire Center and an independent mechanic and nobody can figure out the issue. I’ve had multiple front and rear alignments, purchased 2 different sets of tires which I’ve had rebalanced numerous times and had my car looked over multiple times by different service pros and it’s still a mystery. The shaking is now in the steering wheel AND my seats wobble (I’m to understand a steering wheel shake indicates a front end alignment problem while shaking in the seats indicates a rear alignment problem) making it not enjoyable to drive at all. I haven’t had a single issue with my 4Runner outside of the shaking so I’m not going to jump at any chance to get rid of it and I’m hoping someone here may have some ideas as to what I should have looked at to fix the problem. I’m taking it to Toyota Service in a week to have my serpentine belt changed and a few other maintenance things done and while it’s in the shop they’re going to checkout my rotors to see if they may be warped to a point that they could be making my car shake all the time instead of just when I step on the brakes. Outside of that I have no leads as to what I should have looked at so if anyone has any suggestions I’m happy to hear them. Thanks in advance!