My iphoe 6s has stuck on apple logo. plz help me what to do. i have already tried turning it off many times but no improvement. every time red battery came n after some time same logo appears n no progress. plz anybody help me

Please follow these steps

If your iOS device restarts or displays the Apple logo unexpectedly - Apple Support

Try Recovery Mode:

Turn off your iOS device.

Connect the device charging cable to the computer only (not to the device yet).

Open iTunes on your computer.

Press and hold the power button on your device and don’t let go.

Connect the cable to the device while keeping the power button pressed down.

Wait until the computer detects the device and wait for it to restore.

Restore as New first and then restore from backup if desired.

https://support.apple.com/en-us/HT201263

Maybe your 6s Battery is Defective So due to that Boot-Loop may occur best thing is take it to Apple Store & Get your Phone Replaced because 6s is still Under Warranty