Touchscreens work by sensing electrical changes from your finger. If the software handling those signals hangs, the screen feels dead even though the display itself is fine. That is why a forced restart fixes so many apparent screen failures.
Temporary freezes often follow a heavy app, a low storage situation, or a device that has not been restarted in weeks. The processor is busy and stops processing touch input for a few seconds, making the whole phone feel stuck.
Water, screen protectors and thick gloves can also reduce touch sensitivity. A cracked protector can trap phantom touches or block real ones, producing a screen that seems to ignore you or presses things on its own.
If the display shows lines, blocks or nothing at all after a drop, the damage is probably physical. But if the picture is normal and only touch is missing, software is still the most likely cause.