Yes! I know what you mean and it happens to me all the time. It's such a weird feeling, the energy in the room just seems to get heavier and it changes all together but most of the time I can't get anything from the entity. I don't know if its the same with you guys but ill be laying down or meditating and i'll feel the pressure in the room change when someone comes in. Everything just feels different and usually I can hear like a slight ringing in my ears, maybe i'll feel spikes running up or down my spine. SOMETIMES I can see them but its not like if I was looking at a person...to me....they look more like a concentrated ball of fumes (sometimes they're kind of in the shape of people). Almost as if you were looking at gasoline but not the same consistency...if that makes sense?