Welcome to HealthcareMagic.
depends on many reasons , as in age , stress
, any trauma , or any anxiety
/ a psychological distress in childhood , etc . it can also be due to some brain related issues too . Can i know your age? and if you had any trauma ? or are you an epileptic ?
If none of the above , I would suggest you to meditate, keep calm and follow a good diet and have a good sleep , this develops concentration as well as increases the memory, also you could take a multivitamin
like DIACOBOL PLUS, have lots of greens, vegetables and fruits, if you still have problems , lets take you further with an evaluation, do write back to me with your feedback, and do not worry
Wishing you good health.