no turn over, oil pressure bouncing

Ok guys.. been a while since I've posted something productive...

This morning.. went to go to work and got in the Jeep... truned the key.. lights, fan, radio all came on, but no turn over.
turned key to off.. sat a few seconds, same thing.
did this 3 times and finally it started up.

The starter and alternator are relatively new compared to the rest of the XJ... 2 years old.

What should I first look for, other then loose wiring?

Second.... my oil gauge is bouncing around from 0 to normal running pressure. sits at zero for a while and the check gauges light comes. I have repeatedly check my oil level... it hasn't moved...so is it just a bad sending unit? Pump?

Third... went on a trail ride this past weekend.. and going thru a pretty rocky section I looked at my temp gauge and it was reading roughly 225F... plenty of fluid, nothing blocking the radiator from the front... fans were kicking on...
I need some ideas as what to look for.

thanks all!!

Get a bettery terminal brush. Remove the cables from the battery, clean both the terminals on the cables and the posts on the battery, and replace.

Thanks Eagle. I'll do that tonight at OneTons...