To dream that you are sleeping indicates that you are not feeling stressed or bothered by the issues in your life. You are calm and relaxed. It may also imply that you are refusing to acknowledge that issues exist.
If you are sleeping with a stranger then it denotes that you are trying to elude some circumstance or person that this stranger signifies. It is possible that there is some characteristic inside yourself that you do not want to acknowledge.
To see others sleeping usually refers to some aspect or characteristic of your own personality. It may mean that you are or aren't aware of a certain issue in your life.
Sleeping can also represent death because it is symbolic of endings and fresh starts.