[Aukutsutsu]

This problem is caused by the way in which capacitive screens work. It is hard to understand unless you have had experience with electrical engineering, but I will try to explain it in a simple way.

The non-conductive surfaces you speak of (especially beds with sheets, styrofoam and plastic) are all capable of maintaining an electrical charge. When the phone is placed on this surface, the phone will also pick up this charge in the plastic case/glass screen. This excess charge will affect the capacitive screen because capacitive screens rely on electrical charge to work. When you pick up the phone, you are grounding the case (because skin is conductive) and removing the excess charge built up on the case/screen of the phone, and the screen will function normally.

Edit: Sorry forgot to say this is why only some people experience the issue and others not. The problem is COMPLETELY dependent upon the environment (surface charges, etc.)