Iphone 6s plus orientation not working

I am facing few bugs in my newly bought iphone 6s plus. Sometimes orientation takes too long to change.

Say, if I am in landscape mode and hold the phone in potrait then it takes time to change the orientation. Approx time taken would be 5 seconds.

Also when I use the soft key bubble to launch app switcher, it takes too long to launch app switch typically 5 sec.

When the phone is locked and if I try to unlock then it takes long to unlock the phone Approx 5 seconds.

Note: My orientation was never locked.

These issues are suppressed once I restart the phone. But again start coming back after a day.

My iOS version is 9.0.2 which is the latest available.

Please let me know how to fix these bugs.