My body temp is higher than normal at night during sleep, one time in the 100s. I'm a healthy 30 y.O., no smoking or drinking and my BP is fine. Why?

Diurnal variation. Human body sets it's temperature levels so the lowest (normal) temperature is in am, & highest (normal) temperature is at night. Normals vary among individuals, but in a given individual the temperature setting is rather constant. So your normal is 100 at night and perhaps 98 in am. Someone else maybe 96 in am & 98 at bedtime. See http://www.Unm.Edu/~lkravitz/article%20folder/thermoregulation.Html.
Don't check it. There is a natural variation in body temperature between people and thermometers can also be inconsistent. 98.6 is a very loose average and many people are often in the 96s and several on the higher range. If you are not sick or have a disease for which temperature should be monitored, there is no reason to check it.