Shivering. My mental motivation.

From past one year my body shivers a lot while picking weights in gym even with light weights. Last winter I notice this problem when I was holding a cup of tea my hands started shaking. Initially I thought it is due to cold whether but now my friends also started noticing this issue in me even when try to do exercise with light weights. I don't know for which kind of doctor I should look for or what precautions I should opt to stop this happening. I'm working in night shift from past 3 years which has imbalanced my diet and sleep pattern But I have no other suitable option and can't change job any time soon. Please help As from past few months i have stopped loosing weight, less strength because this issue of shivering is effective my mental motivation. Thank you