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The sensations of vibrations are due to muscle fasciculation or twitchings. these can be due to stress, low calcium levels, dehydration, caffeine overdose or due to more serious conditions affecting the nerves and muscles.
In your case, it is likely to be due to stress.
Besides the multivitamin, please also take a calcium supplement and adequate fluids. Gatorade will help replenish any electrolyte deficiencies you may have.
But if you are in a lot of stress, the vibrations will recur.