Car running too cold

I ve see
I had that problem, but only in the winter. I put a piece of cardboard in front on the radiator that blocked about half the airflow. Car warmed right up t normal. I see truckers restricting the airflow on there big rigs when its cold out, so I followed suit.
Seen this done for all my life, tractors, older ford pick ups, even did it my self on
a hot 406 sbc pick up w/ an oversizes rad/ in it .