99 Honda Civic won't start

that sounds like the starter motor bendix spring not returning , some starter motors can be repaired but most are mostly replaced, if you can get to the starter motor easily try tapping it with a hammer , this could help release the bendix until you get new motor

does it crank at least? possible issues.. Battery, starter, fuel pump, clogged fuel filter, spark plug and spark plug wires, distributor, igniter..

Tapping the starter is just a test,then you replace it as you did

So the starter issue is resolved

No check to see if you have fuel pressure at the motor
when you cycle the key

Also check for spark or injector pulse when cranking

If you have a relay for starter switch it with a similar one

Check fuel pressure with a gauge on the motor
Check volumn as well

See if the fuel pressure holds KO/EO

Sounds like a starter. next time it does it try to tap on starter with screw driver handle or hammer handle just a couple taps then try to restart car if starts then starter is going.

try chage the gas filter i had the same problem and when i chaged the filter it fixed everything

Check starter. Or look at the very small wire going to the starter to make sure it is still connected.

That flap is automatic the choke. Not the throttle. Cleaning it should restore normal operation. Avoid spray plastic parts if there is any such as plastic bushing used in carburator linkage, other than that I cant think of any bigger underlying problem. Avoid prolonged high speed on rebuilt engines untill its broken in(500 miles)

check your solenoid on your starter, usually when it get hot it fail until it cool off. a sign of starter going bad if you have to wait til the starter cool off before you can restart the car again. also check contact to the starter. if you having problems getting the starter to work you can get a small hammer and lightly tap the starter, 90% of the time it will kick over.

if this problem persists then you could check a few things on it, like on the times when its not even making a noise when trying to turn the key, use rubber/wooden object and tap the starter motor but not touching the contacts on the back. if this amkes it spring into life then it will be your starter motor if this does nothing then it will be a dodgy battery supply. does it also make like a screaching noise while trying to start? if so then definitely your starter motor