2016 Ford fiesta won't spin over in the cold

The car won't spin over in cold but as the ambient temperature gets to around 50⁰ F it spins over and starts right up it has a new starter battery has been checked and is good start relay checks good fuse is good ECM is good so my question is what sensors would prevent the car from turning over in the cold I took a heat gun and warmed the fuse block the ECM and the connections around the ECM and battery and fuse block with no results but I can take a small electric heater and place it under the hood with a old comforter over the hood let it warm the engine compartment and the car starts ??? Help please

Bad battery onto bad loose hardware connections going to the starter from the battery. Weak battery issues come up in cold weather - corroded contacts show up too. You did verify that the relays are OK?

IT doesn't sound like "hydro-lock" or anything else too exotic - just some loose bolt that when cold - since things shrink in colder weather - the bolt (or connection) loses contact on the wires that would work when it's warm. Also, to have some corrosion that prevents the full contact being made when cold or icy weather - water does not conduct as well as a solid when as a liquid for the ability of the suspended minerals - can help with conduction.

Might be better to keep a battery charger on it for overnight - get a charger with a meter on it so you can view the "draw" and charge level - for if the battery is OK, but the system connections are not good, the charger would be able to show good charge fully charged to the battery - then you know the electrical storage side is OK, the Electrical Delivery system is not, as if it continues this - then you know you have faulty wires and even a weak starter solenoid - then you'll have to replace the starter (solenoid is integral-intergrated into it) and its cable to be sure as part of this diagnosis - it's (Repair is/may) not over but is one of the next steps to do.