Cars can have many triggers. If you react when you're in a car, then consider these tests. Try each one, and see if it makes a difference. See car triggers and car triggers - treatment.
Tangible trigger tests:
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Airborne trigger tests: Sit in your car, engine off, wearing a mask that is a N99 or painter's respirator (not N95), plus full-body clothes, gloves, goggles, and a hat. Don't touch anything. Does this make a difference?
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Contact trigger tests: Same as above, then remove the gloves and touch everything in your car.
Intangible trigger tests:
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Stress trigger tests: Try the above protections, while driving safely.
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Energy trigger tests: Try turning off Bluetooth, WiFi, and any other electronics. Try driving on a leisurely weekend versus a hectic weekday. Does any of this make a difference?
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Vibrations: Try driving on a smooth road versus a bumpy road. If your car has engine stop-start, try deactivating it because it can cause unusual vibrations.
More tests:
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Be a passenger: Try these same tests, while having someone else drive you.
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Try another car: Try these same tests, while driving someone else's car. If possible, try an all-electric car because this can help rule out many of the gasoline-engine aspects.