the thermostate isn't sticking
My 2008 mazda is running hot just some of the time..water pump isn't leaking and on 2008 Mazda Tribute
might check to see if cooling fans are operating. turn a/c on, see if fans operate. if do turn a/c off and run engine till starts getting warm see if fans kick on before it gets hot. if fans don't come on try tapping on fan motor. if still not working, take to shop have checked.
poss blockage in radiator or cooling fan issue