If someone suffocates or is suffocated, they die because there is no air for them to breathe.

If you say that you are suffocating or that something is suffocating you, you mean that you feel very uncomfortable because there is not enough fresh air and it is difficult to breathe.

You say that a person or thing is suffocating, or that something is suffocating them, when the situation that they are in does not allow them to act freely or to develop.