I get an internal vibrating and twitching and it gets horribleunder stress, concentrating on the computer or after a carride. what causes it?

Vibrating/twitching: Anxiety is one of the causes based on your limited description. For further suggestions, please describe it in more detail.

Stress: If the symptoms intensify when concentrating and driving, possibly stress-related. I'd recommend consulting your physician to r/o medical causes. Then referral to a therapist who uses relaxation and/or biofeedback techniques may prove helpful. Energy psychology techniques are also helpful for stress.

Incomplete questions: Need to know details of feeling? Also, what brings this feeling on and what else is it associated with....I.E. Light headedness, dizziness, pain anywhere, etc.... Thanks for the details; perhaps i can help.