Ok, so this is my situation:

Engine is D15B7

Car will start perfectly when cold and in very cold conditions. Now, after driving for 10-15 min until the engine is at operating temperature, I'll turn it off. I am able to start it back up immediately no problem. But, if I let it sit for 20+ min or so, it will be hard to start. I have to crank it for at least 5-10sec then it will start at very low rpms then reach normal idle eventually after 10sec or so. It will start normally after sitting for ~3-4 hrs. No CEL.

Known issues:

These were happening prior to the hard start issue.
-Random misfires only when cold. After engine warmed up no more misfires. (been like this for awhile)
-Guessing very minor head gasket leak (very little amount of white smoke from exhaust)

Things I have done so far:

-Main relay is good, fuel pump comes on etc
-Flushed coolant (Honda brand) + new hoses + thermostat
-Replaced ETC sensor
-Replaced spark plugs, wires, distributor cap + rotor

Possible causes:
-leaking fuel injector (but the exhaust isn't black when it starts up after the hard start)
-coolant in cylinder (when I get it to start I don't see much or very little white smoke)

I'm not sure what to do. I thought I'd post this before I take it in. I appreciate any advise. Thanks

 

Possible weak spark (dizzy problem) and/or leaky injector as you mentioned.. someone will chime in..

 

for the record, my culprit was the head gasket.