Hi Mate there can be a number of things that could be causing the issue,
Solution 1. Restart iPhone and then restore it
You can try these steps below to put
1. Try another USB cord.
2. Restart your computer for a try.
3. Hold the power button, it might restart your iPhone.
4. Update your iTunes to the latest version. Plug in your iPhone.
If iTunes can't recognize your iPhone, then in iTunes in the top left corner click help > run diagnostics. On the box that comes up, check the last two things. Click next and it should identify your iPhone and then restore it.