Dell Precision 7510 startup process issue

My new Precision 7510 has strange behavior of startup process. When AC adapter is plugged, my laptop starts normally:
- Power button sets on
- keyboard light sets on
- Dell logo appears
But with unplugged AC adapter (and at first run after plugging it again) the laptop starts in a different way:
- Power button sets on
- Caps Lock blinks once
- Power button sets off (seems the laptop is turned off completely)
- Power button sets on again after short period of time (about 2-3 seconds)
- keyboard light sets on
- Dell logo appears
BIOS was upgraded to the latest version (1.10.7), but even after downgrading it to the preinstalled version (1.06.6) that behavior stayed the same.
I've reported a request but the customer support does not help me with it. Does anybody have such the issue?