Rough engine start 2000 accord

Own a 2000 Accord EX; 100k…runs great and smooth 99.9% of the time. However every once in a while, like maybe once a month or so it starts, but sounds and feels like its firing on 3 cyl…will die if I try to put in gear, or take foot off accelerator. If I shut it off and try starting it again same thing will happen. However if I let it sit awhile (sometimes one hour sometimes next day) it will start smoothly and run beautifuly. Problem seems unrelated to temperature, weather, time since last use, stage of the moon, engine temp, parked on hill or flat road. or who tries to start the car… I’m befuddled… any thoughts?

Is it caught up with the basic maintenance listed in the Owner’s Manual? Check engine light on?
Get the engine computer scanned for pending error codes.
It’s likely due for spark plugs and fuel filter. Valve adjustment, if applicable.
If all that checks out I would get a compression test and fuel pressure test.

The problem might be caused from a dirty/defective Idle Air Control valve. This valve allows air into the engine past the closed throttle plate anytime the accelerator isn’t depressed. If this valve fails to go the proper position for the idle condition, not enough air enters the engine which causes the engine to run rough. When you have your foot on the accelerator you’re allowing air into into the engine past the open throttle plate and thereby substituting for the sticking/malfunctioning Idle Air Control valve. Also, if this valve doesn’t go to the proper position when the vehicle is put into gear, the idle will be too low for the load impossed on the engine when put into gear and the engine will stall.

You can try removing the IAC valve to see if deposits are causing the valve to stick. If so, clean the IAC valve and the idle air bleed port on the throttle body with an aerosol throttle body cleaner and reinstall the IAC valve. If this shows no improvement then IAC valve may be defective and requires replacement.