I agree, have your battery and connections checked. Even though it's only 6 months old it could be defective. Also, a drain on the battery is possible. Do you have any aftermarket accessories on your vehicle? A non-factory stereo or alarm system?

 

You can buy aftermarket Block Heaters.
Some go in line with your lower radiator hose while some are in place a Freezeout Plug.

5 degrees F pretty cold if you are running 10-40 Dino oil

 

Which you shouldn't be running in that cold of temps anyhow. GM recommends 5w30 for all but the hottest climates in these engines so oil shouldn't be an issue.

 

I have a 97 4 door 4x4 originally owned by Enterprise rent-a-car. I have found a cord on the drivers side of the engine compartment but have never followed it to see where it goes. My friend had a 2000 and he was the first one to tell me about the engine block heater. He plugged his in every night it got below freezing and never had a cold starting issue. I've owned mine for @ 7 years and never had any problems in the winter until the past couple weeks and it's only been in the mid 30's so far. This morning it was 25 and it refused to start at 5am. I am going to check on this plug today and will report back.
I haven't seen any reply's about fuel pressure either. Low starting fuel pressure could indicate a low battery but could also point to other problems; failing pump, clogged filter, leak in fuel lines
This is a post I read on another forum:
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
I think all of this points to low battery amps due to cold, cant give pump enough pressure to get fuel through injectors therfore no start
Also, when mine does finally start it idles pretty high for 5-10 seconds making me think there is extra fuel built up in the injectors or the filter after all the cranking
just a thought, i'm no pro

Hello, I'm pretty new to this site so still learning. I posted some things I know about this problem, it's happening to my 97 right now. I am checking to see if the cord I found leads to a heater and will post back. My post is on the second page of this forum.