2008 F350 coolant temperature gauge problems

I have a 2008 f350 6.4 superduty and the coolant temperature gauge whem i drive long distance the gauge start working good but sometimes it just go high in a second and said reduce motor power, so i stop and close the key switch and them start up again and it go normal, what can be???

Pd: whem the coolant temperature gauge go hot the truck doesn’t seen like it be hot just a normal temperature