Hi Umesh Mane
This is very generic and difficult to say but I can suggest you to worth checking
1.Heavy After Startup Microflow: check whether startup is there if yes then remove and check , if you see improvement then later on fixes can be done.
2.Multiple Java actions and Marketplace dependencies: Mendix needs more time to,Compile Java,Sync database,Load metadata
3. Scheduled Events Running at Startup: Check this also!!!
4.Database sync: sometime if your application have huge number of tables and relationship yo can face slowness.
If this doesnt work kindly share the logs!!