Why does my left arm and left left sometimes feel light and weak?...i suffer from anxiety but i'm not hyperventilating?

Recurrent true weakness of the arm & leg on the same side raises concern for opposite side cerebral cortex pathology such as blockage in the carotid artery or an intracerbral artery. . A neurologist is best to determine the cause. Appropriate testing will be done.

After you receive the appropriate medical tests, please get your anxiety treated. A clinical psychologist can help you learn strategies to manage it. Peace and good health.