It is actually quite normal for the body temperature to rise and fall somewhat over the course of the day and the night. For example, most people have a lower body temperature while they are sound asleep then they do during the day.
However, it is generally not normal to feel uncomfortably and intermittently hot and cold during the day, especially if these sensation are interfering with your normal day to day functioning. If the problem persists, I would recommend that you talk with your primary care doctor
about the issue. They will be able to perform a thorough physical exam and help determine whether or not this is something that needs further workup.
For example, an alteration in the normal functioning of the thyroid gland, which regulates the body's metabolism, could produce episodes of feeling intermittently hot and cold. There are often other symptoms as well, such as change in weight or mood, and changes in the hair or skin. The problem can be easily ruled out with some simple blood tests.
In middle aged to older women, another common cause of these symptoms is the start of menopause, which involves periodic dilation of blood vessels in the skin and flushing.
Start by seeing your primary care doctor for advice!