Why does the seatbelt light on the dash turn on and off once and awhile?

What is your question?

The seatbelt light that goes out when you latch the seatbelt turns on and off every once and awhile. Usually shortly after the vehicle warms up from not being driven. Other times when the road surface becomes bumpy and you get vibrations thru the vehicle. I really can not figure why it does that when the belt is securely latched?