My arms feel heavy and weak. no activity to cause this and it's been a few days.

Weak and heavy arm: Knowing your age and risk factors would be tremendously helpful in helping us determine the umbrella category. A cervical disc pathology/herniation impinging on a nerve can do this, less likely brachial plexus pathology, should etiology, or cardiac ischemia and several others, even malignancy of the breast or elsewhere given the female gender. I hope it goes away asap as most things do.