Hello,
There could be several reasons behind these. Please check them in following order
1) Shutdown the current startup process.
2) Ensure that a supported version of Java is installed per the Technical Requirements page and this Java version is set in the environment variables appropriately.
3) While this should be the case, but please verify if port 4503 is free by running netstat -an | find "4503".
4) Ensure you have enough disk space/RAM available.
5) After the basic checks above, please check the logs in crx-quickstart/logs directory. The logs most helpful for this issue would be the stdout.log, stderr.log and error.log file. Please look for any errors in these files.
Thank you,
Aneet Arora