@Saurabh Sakpal
Can you please let us know how many nodes are theyr in your cluster?
Also can you please share your ambari-server.log from starting the ambari-server so that we can check at which point ambari server is taking longer time to come up.
Sometimes it happens if the Ambari Server has lot much entries inside the ambari DB (usually old ambari cluster has a lots of old operational logs) which causes slowness.
So please check if you can try purging old ambari db entries using the utility mentioned here: https://docs.hortonworks.com/HDPDocuments/Ambari-2.6.2.0/bk_ambari-administration/content/purging-am...
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Similarly sometimes it happens due to less heap setting of ambari server. So please refer to the mentioned tuning article to see if your ambari server needs some tuning:
https://community.hortonworks.com/articles/131670/ambari-server-performance-tuning-troubleshooting-c...
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