Why do I feel numbness on my hands or fingers?

Carp tunnel syndrome. Numbness of the hands can be due to carpal tunnel syndrome/or nerve damage at the wrist, especially if you spend a lot of time on the computer. It is also can be due to radiculopathy/or nerve damage around the spine. Polyneuropathy is also a possibility. It is very important that you see neurologist and have a few tests done, especially emg, electromyography.
Many possibilities. Numbness can occur from various reasons. Some potential causes include vitamin deficiency, nerve damage, nerve compression, alcohol over consumption, side effects of different medications, or as a result of different systemic medical conditions such as diabetes. Get evaluated by a professional to determine the diagnosis. Treatment is based on the diagnosis.