Lincoln navigator oil/temp light came on. Light off now. All guages are norm. Any suggestions on why light o

Assuming you are not overheated or low on oil (you checked, right?) it is probably a failing sensor.

First check the oil. If, it OK then it may have just been heat. Check the Coolant Reservoir Level.
Not sure of the year model. But, did it do this when moving or stopped? Moving it could be the Thermostat stuck so in time may be needing replaced. If, it do this when Stopped then it could be Thermostat ''OR'' Electric Fan on Radiator. Usually you will see the fan run in a short time just parked and hood up.

Check the oil level. l oil level is correct u should also check the oil viscosity, if is ur last oil change is been over the 5,000 miles u will probably need an oil change. The other reason for the light to go on could be if u run the vehicle without heating first & the enviromental temperture was under the 50 degrees. To avoid the to happen in the future u should warm the vehicle for at least 5 min. before runing it. But if the problem persist, u should take to a mechanic.

since it really could be almost anything if it only happened once l would not worry about it you may never know why. But l can tell you it would not have anything to do with going 5000 miles without an oil change you can go 10,000 miles on an oil change not recommended but you can and you should never let your car sit for 5 minutes and warm up there are some weired people on here that probably answer questions and do not even own a car.