2001 GRAND AM GT - Issues with starting

[NOBODY]

Hello there, this is my first post on here I just joined recently.
Please forgive me if I didn't post this in the right place, I'm not really good with forums.
I've been trying to Google this issue but because I don't know what is specifically wrong with my car it's hard to pinpoint.
I recently bought this car (November 2021), it is now March 2022. This issue has been getting worse and worse.
I took it to a mechanic and spoke with a handful of my mechanic friends and nobody can pinpoint the issue, I'm going crazy here.
This car is a really good car for a 21 year old car and I really do not want to get rid of it. It drives pretty good.

A little bit about the issue:
When the car has been sitting over night, it starts up great! She drives pretty good and everything.
When I drive the car for 5 minutes (Example: when I go to the gas station down the street) and turn the car off, come out 2 minutes later, my car starts like crap.
Sometimes it stalls as it starts???? (I don't even know how that's possible)
The car is not overheating, I always keep an eye out on the gauges and they work fine.
My tank is usually full of gas, I keep it over 3 quarters of a tank.
I fuel up with 87 regular.
There are lights on the dash but they are for Service Vehicle Soon, ABS and Traction (because the previous owner rigged the wires on my front passenger tire when they rubbed against the brakes - mechanic told me this)
There is no check engine light.

All the work I've gotten done to it so far:

• Replaced ignition switch (and everything that goes along with it)
• Got a brand new battery (Optima Yellow Top)
• Got my spark plugs and wires replaced
• Got an oil change at Jiffy Lube
• Filled coolant

Something to note:

• I drove this car from November 1st 2021 - January 2022 not knowing that the car didn't have coolant in it, the previous person had water in there! Once the mechanic put coolant in it, it started driving much better.
• Issue can be replicated 90-95% of the time.
• Issue can be replicated fairly quickly.
• I recently was living in my car in Illinois (in winter time, I had to stay warm) so the car did idle quite a bit.
• A mechanic told me I have a "blocked heater core".

What I was told it could be:
Starter - but many people say it can't be the starter because it cold starts just fine
Ignition Coils
Fuel pump

I love cars but I do not know the mechanical aspects of a car and I'm a female so I'm afraid of going to a shop and getting ripped off.
Can someone please point me to the right direction?
I figured I'd come to a place where people know a little bit more about my specific car / potentially had the same issue?

HERE'S A YOUTUBE VIDEO OF A COLD START VS A WARM START ABOUT 40 MINUTES LATER

Any advice or information is truly appreciated! I am so lost and defeated at this point. I am going out of my mind!!!!

 

[melsg5]

Have any of the mechanics checked for codes since you have a Service Engine light on?
How often do you have too add coolant?
Is there any light brown substance in the oil fill cap?

 

[G-937807]

The only codes that pop up is for the front passenger tire electronics.

I only had to add it one time.

No substance that I can see.

 

[melsg5]

Has anybody checked the fuel pressure regulator vacuum line for gasoline?
Does your temperature gauge when the vehicle is fully warmed up show a reading towards the center of the gauge or is it low?
Has anybody done a fuel pressure test to see if pressure holds after the engine is shut off. If it doesn't hold pressure you may have leaking fuel injectors.

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[NOBODY]

The temperature gauge stays at the middle, on a hot day it gets slightly above the mid point and when I say slightly I mean super slightly.

Never done the regulator vacuum line or fuel pressure test!!! I'll most definitely try to talk to one of my mechanic friends about that (someone who has actually seen my car in person) to see if that may be it.... THANKS SO MUCH FOR YOUR HELPFUL FEEDBACK!!!!