Hello,
I've got the same problem since a few months, since I updated to High Sierra. I've updated last week to Mojave, and the issue was still there.
I've tried changing the cable to an official one, then to a licensed one, then I replaced my iPhone 7 with a new iPhone X, then I upgraded the OS to Mojave. Nothing worked.
The other day I did a search in google again, and I found a post speaking about an issue with Xcode. The post suggested as a solution to download Xcode and open it. The first time Xcode is run, it asks to install some components, and some if them are related to iOS. Actually, if iTunes is opened at the time of run Xcode for the first time, installing those support components will close and reopen iTunes.
Since I did so, I haven't had the issue anymore. I hope this helps!