Greetings Bharath_kiran,
Thanks for participating in the Apple Support Communities!
Since you're only getting notifications with Messages, this could be related to a Focus status being enabled or other notification settings. If you're unsure if this is related to a Focus status being enabled, check out the following resource to see if that could be what's occurring: Use Focus on your iPhone, iPad, or iPod touch
If you determine that Focus isn't in use when this occurs, let's check the notification settings. Be sure you don't have a Scheduled Summary set to notify you at certain times of your notifications as outlined below. Check out additional information for notifications here: Use notifications on your iPhone, iPad, and iPod touch
To schedule a notification summary:
1. Go to Settings > Notifications > Scheduled Summary, then turn on Scheduled Summary.
2. Under Apps in Summary, select the apps that you want to include in your notification summary.
3. Under Schedule, tap the Add button to add a new schedule or the Remove button to remove a schedule. Then adjust the time for each scheduled summary you have set up.
We hope that information is able to help with clearing up what you're experiencing.
Have a great day!