My xr’s battery health still at 100% since i started using it last year dec
I usually charge around 30-40% until 80-85% sometimes until 90%

I never let the battery drops below 20%

No

Last night the phone is still fine. When I went to bed, I just left the phone on the table (no charging) and then this morning when I woke up, I want to use my phone but it won't turn on.

I thought the battery is just dead. I tried charging the phone. It does get warm. So, I guessing the charging is still working. But the screen just won't turn on.

I have tried

1. (From Apple website)
If your screen is black or has frozen

Follow the steps for your device.
On an iPhone 8 or later, including iPhone SE (2nd generation)

Press and quickly release the volume up button.
Press and quickly release the volume down button.
Press and hold the side button until you see the Apple logo.

But no response from the phone

2. Connect to iTunes. Nothing show up

Is there anything else I could do?

I afraid that I will need to bring it to service centre. The phone is still in warranty. Will the warranty cover this kind of issue?

1. Yes. Nothing show up
2. Yes. I tried the steps and i can't get it to enter DFU mode. There is simply no response from the phone.