on the freeway 75mph steering wheel shakes
I think you probably have a tire that is either out of balance or is seperating , go to a tire shop and have your tires checked
High speed shimmy is usually caused by wheel/tire imbalance. Have it checked.
Most generally steering wheel shake at speed is due to tire balance. On rare occasions it can be due to a tire with a belt that is broken or defective. Any good tire shop should be able to diagnose and correct it.