when I try to start the server
What server? Is the server running in its own process or in the Eclipse process? The solution depends on the answers to these questions. (The basic solution is to increase the heap size, the "how to" depends on the answers.)
Actually, you could also be out of memory on your machine. That is, the server you are starting runs in a separate process and the amount of memory required by the server exceeds the available memory on your machine. In that case either decreasing the heap and/or permgen size for the server, or decreasing the heap and/or permgen size for Eclipse, or installing more RAM, or increasing the page file size would help.