I put a heater under the truck 1 hour it will start?

Hello,

It sounds like you might have an issue with your crank position sensor.
Crank sensor sometimes gets triggered with temperature change.
It may or may not trigger a check engine light when there is a fault with the crank position sensor.
When that sensor does not work properly it does not send the signal for the engine to start.
So you will just get engine to crank but no start.
The crank sensor is located lower right side of the engine, next to the crank pulley.

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works
https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

I have attached the crank sensor diagrams for your reference.

Please let me know of any questions.

Thank you.