I spent 2 hours researching car seat ergonomics when I got my latest car and struggled to get comfy.  I turned all the research into this guide; maybe it can help you (and anyone else who needs ergonomic help).  No AI was used as a source nor used to write this.  

1. Prepare by flattening the seat pan to be level with the ground, then adjusting the backrest to recline 20° back from upright.  Empty pockets, then sit with thighs and back fully against the seat.  
2. Lower the seat as far as possible while being able to see out.  Eyeline should be in the middle of the windshield, or at a minimum, nose should be above the dashboard.  
3. Adjust seat forward/back so knees are still slightly bent when flooring accelerator and brake.  The recommended knee angle ranges from 120-160° when resting on pedals.  Ensure back is still touching see cushion during adjustment, and whole foot is touching pedal (not just the toes).  If drivers has long legs, can optionally raise the seat, so torso can be closer to steering wheel.  Next, knees should be level with hips, never above them (unless car is old enough to lack seat belt pretensioners, in which case mildly raised thighs avoid submarining during a crash).  Seat pan should be angled so thighs have even pressure along them.  
4. If available, extend the thigh support until there are 2~3 fingers gap to back of knee.  
5. Backrest can be tilted so there is a 100-110° angle back from flat seat pan.   Spine should be supported.  
6. If available, adjust lumbar support until pressure feels the same from hips up through all parts of spine.  The bottom of the lumbar support "bulge" should be at the beltline, or at the bottom of the pelvis.
7. Vertical center of headrest should match vertical center of head.  Alternatively, top of headrest should match top of head.  Headrest should be moved forward or backward until it touches the back of the head when head is straight up from base of neck.  
8. Steering wheel distance: lean back against seat and extend an arm straight outward and upward so it rests on top of the steering wheel.  The steering wheel should be extended/retracted until it is lined up with the wrist, or is marginally closer.  There should be 25~30 cm from chest to airbag (9⅞~11⅞ inches), and airbag should never detonate into stomach or shoulders.  Shoulder blades should always touch backrest, even while steering.
9. Steering wheel height/tilt: Arms should naturally be at 120° angle while holding the wheel. Shoulders should not have to elevate when turning the steering wheel.  Eyeline should be at least 3" above steering wheel.
10. Final adjustments: Adjust slide mirrors so the rear of the car can't be seen.  Adjust rear mirror to avoid moving the neck when looking behind.  Take a break every 2 hours of driving.