My left-hand shakes when I hold a cup. What could...

Dear Customer
Welcome, and thank you for trusting us
tremors has three main causes which are :

• cerebellar tremor
• intention tremor
• basal ganglia tremor .

basal ganglia tremors are resting tremor ,cerebellar tremor are kinetic tremor,which occur when you want to pick object .intention tremor are tremor that occur during movement but during stressful sitiuation .
you may have intention or cerebelar tremors that needs evaluation by neurologist .you may need doing brain MRI to evaluate the status of cerebellum .

Feel free to message me anytime here if you have further question.
It’s our pleasure to help. Please feel free to reach out to me anytime. 
You can also ask our other certified experts in various fields such as: Nutritionists, Lawyers, IT Experts, Therapists, Mechanics, Doctors, Handymen, and more.
Kind Regards