If your voice unconsciously vibrates when singing

If your not aware or conscious of your voice vibrating when you’re singing, more than likely it can be fixed.
If the doctor says you have no obvious problems with your larynx at your local physician or at the Otological hospital, than the issue you may have is asymmetry of your larynx. An asymmetrical difference in motor movement of the muscles and folds of the larynx can cause the voice to vibrate unconsciously, similar to a tense muscle or reflex action.
Specifically, if the right and left side of the vocal folds move asymmetrically, it directly causes hypertonic vocalization. The body goes into a hypertonic state in order to try to correct or force each side to move symmetrically.
When the left and right side of the vocal folds do not vibrate evenly with each other your breath leaks, thus causing a hoarse voice when vocalizing.
If the muscles rotate or slide the arytenoid cartilage, which does not move equally on both sides, the muscles then get tense in their effort to support the left or right side.
Muscles usually vibrate when they show signs of tension, such as the biceps, brachii, or the rectus abdominis muscle.
Similarly, the voice vibrates too, without consciousness of it.
You can find a suitable solution, using this information as a base to understanding which issue you have, combined with having your throat and larynx examined.

Opera Singer