2010 Sonata won't quite start
 

Earlier today, go on lunch from work. Car starts fine. Stop to get food, get back in, key turns but makes a weird sound when I go to start it (like it's trying to start but quieter). It threw me off, so I turn the key back to starting position. Depress brake, find pedal won't depress normally and key won't turn. Car is in park of course. I jerk the wheel thinking the column has frozen, but no. Fiancee comes and brute forces it, fired right up. Runs fine. Fast forward.
Go to leave work 4-5 hours later, put in key, brake depresses fine, turn key and it sounds like it's trying to start but quieter (if that makes sense). Sounds like a normal start but without the engine actually turning over. I am stumped. Thinking either starter or fuel system, but I would appreciate any advice! It's a GLS base model.

Too little information to make a clear diagnosis.

For now, try cleaning up battery terminals/posts and grounding points.
This will make electricity flow better and eliminate corrosion as a problem.
If it still has a problem starting then come back with a little more information

More diagnosing has been done. Battery is reading fine, terminals fine. Lights come on fine, radio, all the rest. I tried to upload audio of the sound, but there is both the standard starter clicking and also the whooshing sound it normally makes when starting that you get whenever turning the key. The engine tried to start at least twice in approximately 8 attempts (done over time so as not to flood the engine), and we could hear it want to start, but didn't fully turn over.

Standard starter clicking??
You mean the starter does not crank engine and only makes the clicking noise??

It tried to start in 8 attempts?
If you have carb cleaner or brake cleaner or better yet, starter fluid then spray some into the intake (avoiding MAF if you have one)
And try starting. If it starts then fuel system issue.

I appreciate the starter fluid idea. Also, in listening back to the recordings I took, it makes a sound like a drill whirring. It does occasionally engage the engine and sounds like it's going to start, but doesn't actually do so. Head scratcher for sure. Hoping the starter fluid will help!

Hold on
The starter is making a whirring sound and engine does not crank??
Then it sounds like the plastic bendix lever is broken or on its way out.
Also could be solenoid in starter that is not pushing the bendix to engage starter motor.
So, now you are making it sound like the starter is no good.

We totally agree! Hoping this is the only problem. Thankfully a local pick and pull had the part and we found a guy willing to do a parking lot replacement, so I will let you all know soon!

Starter replaced and she is running like a champ! Thanks for the diagnoses everyone!

Thanks for the update
Glad you got it working