Temp gage needle suddenly shoots to high and then drops down to normal. this intermittent. No other warning lights. Opened hood and noticed coolant in tank is way below the Min. mark. What might be th

I'd suggest checking the radiator, radiator hoses and other elements of the cooling system for leaks, replace the thermostat, flush the system and refill with new coolant. See if this solves the issue...

Thank you for your response. Could it be a blown head gasket? This seems to be a 2005 Nissan Sentra historical problem! Thanks again.

Could be...some tell-tale signs that would point you towards a blown head gasket would be the car consuming more coolant than it should and getting a bit of a misfire on cold starts that goes away after the car warms up, with or without a check engine light. If the car was going through coolant before the needle issue you're pointed then I'd suggest head gasket but try the thermostat change and cooling system flush and leak check first and monitor the car afterwards....