It can be very normal to have some shivering at the beginning of a presentation, which in fact just demonstrates our initial anxiety and, thereafter, we are able to get over it. It can be related to our predisposition, excessive worry about the outcome or just a normal shakiness.
However, if the anxiety is profound, leading to further problems in speech output, drying of mouth, racing heart and continuous shivering, it would require further treatment. Your psychiatrist / doctor should be able to advise you about the drug which can be taken for short-term relief from tremors if no contraindications exist.
Also, long-term cognitive behaviour therapy along with some medications may be required to counter intense anxiety.
Wish you all the best for your interview.