I guess go back to the basics.....
Fuel
Spark (at the correct time)
And Compression
What I would do is fit an Inline spark tester to the plug wires, and when it won't restart, crank it over and see if you're getting a constant spark.or intermittent...
https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6