Unresponsive / Laggy original touchscreen

Just like another person described, however no parts were replaced, still the original screen and the same problems:

• keyboard buttons don't fire
• Keys will lag and then fire multiple times (e.g., apps starting by themselves)
• Scroll becomes jittery and/or completely unresponsive.

I’ve tried restoring the phone and in the begining looked like it was better, but after sometime, it came back.

It happens in a completely intermittent mode.