Your MRI and routine blood tests are reassuring. However, since these problems are frequent, involve word-finding, attention and recent memory, and are affecting your studies, they deserve a proper clinical assessment rather than simply attributing them to “forgetfulness.”
At 22, serious neurodegenerative disease would be very unlikely. Commoner causes include poor sleep, stress/anxiety, inattention/ADHD, excessive screen use, medications/substances, etc.
I would suggest a neurological assessment with formal cognitive/neuropsychological testing to objectively assess attention, memory and language. Your mildly low
vitamin D can be corrected, but it would not usually explain this entire pattern.