I have restarted my iPhone by doing the buttons as you suggested. The screen is unresponsive to any touch.
My touch screen is no working even after multiple restarts.
My touch screen is no working even after multiple restarts.
Try the other suggestions in here.
If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
I have restarted my iPhone by doing the buttons as you suggested. The screen is unresponsive to any touch.