Sometimes, when i wake up, have hard time recalling what has happened previous day.usually for the first couple of mins after i wake up.what it is?

Many causes: Memory loss may be related to subtle nervous system dysfunction which can be associated with inflammation or from toxic environmental exposures such as toxic mold, chemicals, heavy metals. Thorough neurologic evaluation and brain imaging should be considered if persists or is associated with other neuro changes (pain, tremor, weakness, numbness,dizzyness,headache).

Sleep : If only for a few minutes and otherwise memory is good then likely non specific and not cause for concern. It could be related to poor sleep : do you have enough sleep , ever disagnosed with sleep apnea , snoring , over drinking or over watching screen time before sleep ? Adjusting and looking into those issues could help improve this symptom.