Nail popping on dry wall ceilings and walls are caused by several things.
One being termites. As they destroy the wood members the nails loose their ability to grip the boards thus begin to loosen up.
However, Do not be to concerned yet about that.
If you have a newer home that has truss construction for the attic. This is the framing in the attic areas are shaped geometrically in triangles often smaller boards used. There is a thing caused truss uplift that can cause the nails to pull out. See diagram. The fix for this is to pull the nail out and replace with a new one a few inches away or use a screw. Ideally if the ceiling was properly fastened they would leave out the nails around the outside edge of the room and allow the wall boards to hold the ceiling up in those areas. This allows the ceiling boards to move up and down with the movement of the truss.
Still another reason for nail popping is storage or excessive insulation in the attic. Many people use the attic area for storage. They start with 16 inches or so of insulation then put a large sheet of plywood down on top causing the insulation to compress the press against the sheet rock below that is the ceiling. Add to that the additional weight that causes the ceiling boards to bow ever so slightly and the result is nail pops. The fix is the same as above, pull old nail out and replace with screw. Or new nail about one inch away. Personally I use two nails when fixing this issue about one inch apart just to be sure the issue does not happen again.
Some times it is the fact that they just did not use enough nails to hold the ceiling up. But age and style of home would dictate that. If this is just starting to happen and the house is older, then look for the insects as a first issue. But if the house is newer, 25 years then it is a nailing issue that can be corrected as stated above.
The last reason for this to occur is excessive humidity . To much moisture can soften drywall and cause excessive weight causing the ceiling to sag. In addition excessive humidity can cause expansion on wood joists causing them to move thus additional stress on the nails holding up the drywall.
So there are several things that cause this. Do a little research in the attic above first then move from there to make the repair.
Most of the nails that loosen are from vibration in the house and there is no way to stop it unless you use sheetrock screws which is the best way to secure sheetrock to walls and ceiling.