I noticed when i'm nervous or doing something my head shakes for abt 2 seconds .. and it's been happening randomly thru out the day ... what can it be?

Titubation: Titubation refers to oscillation of the head or an unsteady gait. When involving the head it usually occurs in the "no-no" direction. It can be seen in a variety of conditions including benign essential tremor, cerebellar disorders, or the effects of medications and alcohol. If you can discover any family members with similar features then benign essential tremor is the most likely cause.