Car wont start

Car tries to turn over but just wont start. It chugs and chugs like it wants to start but will not. I let it sit 30 minutes or so then it starts right away and drives fine. I bring it back home, wait a little bit , go back out and it wont start again. I have a new battery, serpentine belt, plugs...car is a 2008 GP basic. 63,000 miles. This has been happening off and on for a month. The shop said everything checks out fine and they are not sure whats going on...no codes being thrown.

Check the fuel pressure at the injector rail. You can rent a fuel pressure gauge at some autoparts stores. If the pressure is less than 45 pounds with the fuel pump running then you could have either a bad fuel pump or a bad fuel pressure regulator. Also check it with the key off. The pressure should hold for a time. If it drops off quickly then the pressure regulator is certainly bad. This is the simplest test to run to see what is happening. If the fuel pressure regulator is leaking through then there won't be enough fuel pressure for it to start.

Mechanic said it threw a code for crankshaft so I assume it's the crankshaft position sensor??? He's going to change it out for a total of $130. Is that a relatively easy change out? I have no idea where it is on the 08 engine

The hardest part of the change is getting the harmonic balancer off. If he wants $130 then let him do it for that. Especially if it includes the part. Worth the price to avoid the hassle.

I had these exact symptoms a few years ago on my 99 Grand Prix GT. I had a bad MAF sensor.(black square looking sensor next to throttle body). I unplugged the MAF sensor and it started right up and ran with the slightest roughness at idle but never gave me a problem again. (the service engine light will come on but will go off when you get a new sensor).I drove it with the MAF sensor unplugged for a few months until I got a new sensor! Hope this helps!