Sometimes, the tip of a specific finger will become a little numb. it usually happens when im writing, but occasionally it happens when im not (it could be because of pressure like when im writing, but i cant be sure). what could cause this?

At certain position of the hand, wrist or the elbow, the nerve or a small branch which innervates that specific finger can be transiently compressed and that event can cause the fingertip numbness. In that case, after you change the body position, the compression is relieved then numbness resolves.

Though likely just local nerve compression, if noted in AM waking may consider carpal tunnel, ulnar impingement or cervical disc disease ( even in younger individuals) . Any weakness or other symptoms like blurred vision may consider evaluation for rare condition like MS. F/u/ w/ MD