Hi,
At the start(when first powered up), BNO055 sensor reads the angle in a wrong way, then the it is calibrated by rotating, afterwards the problem is gone and angle reading becomes correct in the normal condition(no relatively magnetic distortion).
The problem is that when the BNO055 starts(when first powered up) near the something having the electromagnetic field(on the vehicle), it shows initial position as 0 degree, but in the normal condition, it shows the correct angle at the beginning.