Heating up after car is shut off

I have a stupid question to ask I have a 69 318 when I shut it off it climbs to 210 to 220 but I soon as I restart it the temp jumps back down to 190. I also have a 67 that has a 408 stroker and doesn’t do that when you **** it down. I use an electric gauge in the 69 plus the temp gauge in the dash. The motor has been rebuilt and I have fought heating issues. I use an aluminum radiator for both cars along with a mechanical fan and shroud. Just curious why it does that. I run a 191 thermostat in both cars.
Pat Faley
67 notchback
69 convertible
East Peoria IL