I start the car and after a few minutes of driving it overheats. The temp gage goes up to the red, stays for several seconds and it drops down to normal temp (half way). It then stays normal for the rest of the trip.
My car has 100000 miles.
My car has an automatic transmission.
There are two principal possibilities that would explain what you are seeing. If the dash gauge stays in the overheating (red) zone for literally seconds, that would suggest that the gauge, sending unit and/or wiring has a fault. Typically, if an engine is really overheating, the overheating is not resolved within seconds and so a "gauge-related" malfunction would seem a strong possibility. It is also possible to have a sticky thermostat, but the stickiness is probably not such that engine temperature, as you indicate it as reported on the gauge, would fluctuate as rapidly as you report. I would recommend requesting a diagnostic on the temperature gauge which would include consideration of whether the engine is even overheating, too. Note that using an ordinary infrared thermometer, applied at the right areas of the engine, will give you a basic idea as to whether your engine is running too hot or too cold. The bottom line is if you request a diagnostic on the gauge, a certified mechanic will get this promptly resolved for you.
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