Explore our TOS forum & stickies there to see if any of it fits..
Posture? forward head & shoulders , hunched /rolled shoulders ?
Other factors..
Desk work, sports, hobbies, phone, gaming, computer..
Past whiplash
Repetitive work , previous RSIs

and xray/MRIs to check for bone anomalies or extra cervical ribs..

Best to find out if TOS or not before any surgery, some had carpal tunnel or cubital tunnel surgeries only to find out later when symptoms were still happening, that they did have TOS and probably didn't need those other surgeries..