Q.holly has many branches with leaves only at end
What should I do with my small holly bush that has no leaves except on the end of branches? This is mainly in the center of the bush.

This could be due to a few reasons.
Insect or fungus issues.
Sun scorch can cause this.
Lack of sunlight reaching the center of the plants.
Here are some links for you to pinpoint the issue.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/leaf-scorching-in-holly.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/fertilizing-holly-bushes.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/trimming-holly-bushes-how-to-prune-holly-bushes.htm