I see a few flaws in your thinking.
You mean Crank but not Start (turning over is cranking)
It would be nice if we knew what you tried.
You got a Check Engine Light ---Then What --Codes do not tell you
what is wrong or what to do.
I have been explaining that not just there but for the last 25 years
What Codes? Have you Googled them & read up on possible causes & solutions,
& how to system & component test things ?
I may be wrong but did you replace the head gaskets yourself not many folks do
they pay a repair shop.
Why would Spark Plugs be an issue ?
The Plugs would be new when the heads went back on & if you have any kind
of maintenance schedule they would be due or not due,not like they failed,
they wear & stress the ignition system.
The Answer is NO --- No Parts Ever Get Changed until you find a Problem --Period.
You Do Not Throw Parts at a Vehicle Problem --You find the System with an issue,
then continue your testing to system components,replace a needed & then retest
everything all over again to confirm the fix.
Second Answer --- You Need Professional Tools to look at the Data & then Test
On the side of Logic -- I give you that one.
Waiting For Sensors to cool off -- maybe
Crank Sensor,maybe another sensor -- but not on a guess & wish & hope strategy, because
you can afford the parts.
What about Fuel Pressure,Ignition other than sensor or plugs
Ever think the Fuel Pump may be worn electrically or mechanically & won't start every time.
Using that logic & some testing you could have a several possible causes of a Symptom
You have a Symptom to Diagnose,not a problem,it will be when you find something amiss.
Cam & Crank report to the same module maybe, but don't exactly work together & even you
can't believe several sensors or a list of items all failed at once !