NOTE: THIS SOLUTION IS POTENTIALLY DAMAGING AND MAY NOT WORK FOR EVERYONE
PROBLEM: touch screen acts erratic, notification bar keeps opening, screen appears to be touched by someone else continuously (Ghost Touch), and parts of the screen DO NOT RESPOND TO TOUCH.
MY OWN SPECIFIC CASE: I had the Ghost Touch issue for 3 days suddenly without intro, which often used to go away after a reboot or two, then phone worked normally after I removed the battery and left it in a dry area (in a closed drawer between books, no air entering, very dry atmosphere), however the RIGHT SIDE of the screen (Search button, rightmost letters [L and Delete and sometimes ENTER] do not work. If the phone is in normal landscape, you cannot open the notification bar by dragging it normally.
DIAGNOSIS: for some people, the problem is more severe. The Digitiser itself could be malfunctioning and has to be fixed, while for others it could be a true problem with the screen itself. However, for MANY OF US, it is a problem of HUMIDITY. The humidity sensors are causing the phone to act like that. Some say part of this problem happens because the way the keypad affects the phone internally as you open and close it a lot.
1- To be safe: send the phone to the shop. Ask them to open the phone and apply an extra layer of insulation, in case the digitiser and the screen are okay.
2- If something is faulty, replace it at the shop.
3- MY OWN SOLUTION: based on something I read many times, the solution was to apply DRY HEAT for at least 45 mins. What I did, based on averaging out many experiences I read online, was to remove the SD Card and SIM, remove battery, I heated up a toaster oven for 10 minutes, waited until the temperature was at about 60-70 degrees Celsius, SHUT DOWN THE HEAT, put the phone on its screen on a plate, screen facing down and covered by a cloth to protect it from direct contact with metal, then all inside the oven. The oven is a relatively big one, so phone was AWAY FROM A SOURCE OF DIRECT HEAT. I closed the lid, then every while 15 minutes I would heat the oven for 40 seconds to maintain the temp. This is LIKE (ALTERNATIVE SOLUTION) leaving your phone in the glove compartment of your car while its parked in a sunny spot, to find it really hot in the morning and tough to touch for a while. TO CONTINUE, after the phone was out of the oven (I can't believe I am saying this), I left the phone overnight in a dry area for 8 hours (could need less time). Then, I put everything back in, plugged it, and THE PHONE IS WORKING PERFECTLY NOW!
NOTE that solution number 3 could affect your keyboard buttons if heat is too much. It may cause the glue holding the keys to melt a bit. Be delicate with your keyboard after you restore your phone.
Again, I only did this YESTERDAY. With the exception of some keypad stickiness, the phone is working perfectly now.
I hope this was useful
EDIT: Today is the First of May, phone is still working without a glitch
N.B. Press the Thank you button if you wanna congratulate me on daring to toast my milestone in the name of scientific inquiry
SECOND EDIT: Phone did it again for 2 days. Applied the same method, and it worked again. I think partially it happened because I was in a very humid location.