My right hand feel weak somtimes. I can't grip tightly and when I does my hand will be shaking. This is happening only to the right hand. Why?

Weakness. Weakness on one side is concerning.You are younger and that makes more likely a peripheral nerve problem issue.However a central problem such as tumor could be possible. I would see a provider to evaluate this problem.
See below. These symptoms could be serious and need to be thoroughly evaluated by your doctor.