My hours at work keep getting cut?

i just started two weeks ago at golden corral, and i've been scheduled to work 60 hours over the past two weeks. I've worked 15. i drive their 15 minutes early for my shift, but they 75% of the time they tell me we are too slow or we overscheduled. i'm even filling in for a regular employee until they get back next week. should i talk to human resources about it, hope things will get better, or just look for another job?