iPhone
Hi,
If (unlikely from what you describe) there's absolutely no way the device is pressed against something that could power it up then you have a faulty iPhone. As a veteran of faulty iProducts I am sadly familiar with the frailties of anything made by Apple. Incidentally, the whirling kaleidoscope is known as a SPOD (Spinning Pizza of Death) in the trade as it usually signals expensive grief or at the very least a need to reboot.
You mention your 'phone is fairly new so it should be covered by at the very least the statutory guarantee. Try and steer clear of going to an Apple outlet and the comedy 'Genius Bar'.
Good luck.
Marc