2000 Volkswagen Jetta car problem!

Hello, I have this car, all the fluids are okay, but every time when I start the car a temperature light show up, and a sound, after I start driving about 5 to 10 min. The light is gone. I change the temperature sensor but that is not the problem; could you help me to figure out what is the problem? Thank you in advance. Hope you can help me, because the snow it's coming soon and low work so I want fixed before, and I do not have too much money to take it to a car taller. Thank you again ;)