Hello ABC_001,
Welcome to Apple Support Communities. We're glad you're here, and it will be our pleasure to assist you.
We understand from your post that your iPhone is running low on storage space, and you've encountered an anomaly when it's connected to your computer.
First, we suggest following these steps about How to check the storage on your iPhone, iPad, and iPod touch, which includes tips to free up device storage.
Also, be sure to make a back up of your data before you proceed: How to back up your iPhone, iPad, and iPod touch
If you need further assistance, please post back with the following details:
- Which type of computer are you connecting to?
- Is the computer running the latest OS version?
- If you're using a PC, have you installed the latest version of iTunes? Download the latest version for Windows.
- Do you see your iPhone in the sidebar of iTunes or Finder?
Warmest regards!