Dear Wenda, a person's baseline body temperature may fluctuate quite a bit, depending on time of day, activity level, where the temperature was taken and the type of thermomter used! However, T 38 is a fever, and there are so many causes: maybe viral, bacterial infections, or even some forms of cancer.
I would strongly advise that someone with a fever (especially now with Covid-19), to please check for the nearest PHPC clinic, and call ahead to make an appointment. The attending doctor will need to assess, take a history, do a physical examination, and then advise accordingly.
Stay well!
https://www.gov.sg/article/i-am-showing-respiratory-symptoms-where-should-i-go
https://www.flugowhere.gov.sg/