My Dr Prescribed Nature Throid 65mg But Suggested I Start

My dr prescribed Nature throid 65mg but suggested I start by taking 1/2 the dose. the pharmacist said to take it 4 hrs before eating or drinking anything, so I get up at 2am to take it, after taking it I get heart palpatations and heartburn. Is this normal, should I take it at a different time? Its only my 2nd day taking it.