For no reason my wife eyes are burning her,what could cause that 2 days

Excess body heat can cause burning of the eyes, say due to over-exposure to the sun.
Prolonged exposure to bright light can cause a burning sensation, too.

If there is not disturbance in vision, instilling pure Rose water in the eyes may help.

Sometimes, burning is a precursor of conjunctivitis, or inflammation and infection of the eyes, which would manifest a day or two later. This needs proper treatment by a doctor.