Can you help me with diagnosing the problem with my car?

Sounds to me like a couple of possible issues. #1) Starter is on it's way out-intermittent operation. It could have a 'hot' spot in it and never show up on a tester. #2) Coil or Ignition module could be on its way out-intermittent operation. You should ohm the coil to be sure.

I had something similar occur with my old Camaro. The problem was with the alternator. The alternator was working, but not at the capacity that it should. So my battery was getting constantly drained and then if it "rested" for a day it would have just enough juice in it to start, but after I shut it off it was a 50-50 shot on whether it would start again due to the poor charging the alternator was doing.

Not saying that is the issue, but given the battery, plugs and wires have been changed, the alternator is next in line.

Not enough imformation on this one,next time it happens pull a plug wire and put a spark plug into it and then ground the plug on engine steel/alloy and spin it over,you're looking for a spark at the plug tip.without that I cant go further.

Perform a fuel pressure test - fuel pressure regulator or the fuel pump

Replace the fuel filter

Perform an ohm's test on the ignition coil

Perform an ohm's test on the fuel injectors

Test the ignition control module

starter most likely.

check the compression , then check the timing