Starts fine after sitting idle for awhile but then it won't restart
 

1990 Mazda MPV (manual shift) has been running fine until December. It starts on the first crank after sitting idle overnight. It drives around town with no problems but then I turn off the engine, it does not start again. It cranks over but does not start. Sometimes it needs to sit for a few hours before it starts again. Also, this is an intermittent problem, some days I have no problems at all.

I have had into the mechanic and they can't find the problem either.

I do not know if it is the cold temperatures that affect the starting.
New spark plugs, leads, distributor, timing belt were replaced in 2013.
Any suggestions?

Thank you

Probably the ignition coil. If original it is 25 years old. Pretty much any distributor bought in 2013 will be Chinese made and not the greatest quality so is suspect. You need to check for spark/fuel pressure/injector pulse when it fails to start. The spark should be blue and not orange. Orange is weak spark. Once we know what is missing it will narrow it down.

Cam & crank position sensors can also suffer from heat soak.