Bad dreams

My nearly 3 year old has seemed to be having a few bad dreams recently. Is there normally a stage they go through where they are more likely to have bad dreams? Also Is it likely that they get very hot? Earlier this evening he woke up and he was so hot his pyjama top was soaked through and his sheet was wet, and his hair was wet.
He was very poorly over the weekend and also had a little bit of a tempreture so should I be worried about him getting so hot? Any advice on bad dreams and whether i should be worried that there might be something playing on his mind?