I want to move a TV. It fits in the car but it is not very secure, to the point where if I have to stop quickly, it WILL fly forward and it WILL shatter.
I want to avoid that. How can I secure the TV in the backseat of a sedan?
If you have space to lay it down, do that. This is probably only possible if you can fold the seats forward so the TV is laying both in the cabin and the trunk. Cushion it with soft things underneath and and on top in case something rattles around and lands on top.
If you can't do that, stand it up in the backseat. Cushion it with pillows and large blankets or comforters on both sides. Use the seat belts to hold it in. Most seat belts are built so that the retractor locks if you pull the belt all the way out. It's designed to help install child car seats but it'll be useful here. Pull the belts all the way out and let it back in a bit. If you can't tug it out again, then it's locked. Wrap them around your cushioned TV and buckle them in. Let the belt all the way back it, making sure it stays locked. You can even tug it a little tighter - pulling away from the buckle and helping it retract a bit more - for a snug fit.
The belt will unlock again once it gets retracted enough so it's possible that'll happen here. Add some more cushions to force the belt out more and try again. You should end up with a snug, cushioned fit.
Use the passenger seat belts with cushions.
Make sure there are no loose items that can fly into the TV.
If it is a tube-type TV, lay the TV screen-down on the back seat to protect the screen. Any seat belt buckles should be pushed out of the way. Pull a seat belt and shoulder harness around the TV. If unable to do that, place the TV at the front of the seat so it rests against the forward seat back.
If it's a wide screen TV, protect the screen. If the TV will lay screen-down on the seat and not contact any seat belts, do that, but seat belts cannot simply be moved out of the way. They will rub on the screen surface and damage it. If the TV cannot be laid screen-down, but will lay screen-up do that, but insure nothing will fall on the screen. If the TV is too big to lay on the seat, place the top of the TV at the rear of the back seat and lean the TV forward so it rests against the front seat at an angle.
If you have nothing else in the car with the TV there is no need for any blankets or cushions. The interior of the car provides enough cushioning. Insure the TV does not rest against anything hard.
The question is how to transport a TV; not a bunch of stuff in the car. If other items are carried too, use sufficient padding between items.