I would imagine the sentiments and trepidation is normal, as long as one does not let it take control of their emotions.
I went to PI not too long after Vietnam, and the boot camp scenes portrayed in "Full Metal Jacket" were dead on accurate. I would assume that the physical violence towards recruits is not longer the norm, so that is one less thing to be concerned about. Think of the tens of thousands of recruits who preceded you and made it through, and were better off for meeting the challenge. Recruits are not dying in droves you know.
DI's are highly trained, dedicated and tightly screened for instability or unnecessary cruelty. They told us: " everything we make you do has a purpose". So I set my mind to attempting to determine the purpose of the seemingly inane aspects of boot camp routine. It allowed me to stay centered instead of becoming anxious.
Best of luck.
Former USMC, Plt 2003, Fox Co, 2nd BN, RTR, MCRD, PISC.