Kajal,
Sorry that you are seeing this issue.
Are you working with a large workspace? You might need more memory if you are working with a large workspace.
Can you please try increasing the -Xmx value to a value higher than 768m, ex : -Xmx1024m and check if it helps?
If the machine has more available memory, then you can set -Xmx to higher than 1024m.
If the issue persists even after increasing the -Xmx, please share with the OS and version details along with the .log file located at /.metadata/.log for further investigation.
Let us know how it works for you.
–Swapna
MyEclipse Support