1997 Pontiac Grand Am Temperature gauge

My temperature gauge stays in the normal condition after I turn off my engine, sometimes it goes down completly and other times it stays at about 150 overnight. The car runs fine and the gauge never reachs the hot stage when driving alsio when I restart the engine the needle on the gauge goes all the way down and slowly reaches the normal temp as I drive for a few minutes. Is this normal, my Subaru gauges always goes completly down when I shut that engine off.