98 LeSabre voltage gage variation

I have a 1998 lesabre and when I start the car the voltage is low on the gage. Then after about 4 seconds it comes up to around 13.5 volts.

It also sometimes drops and then returns to normal when I apply the brakes or put the car in gear

any ideas?

Both the voltage and the temperature gauges on my 1999 LeSabre are inaccurate.

I bought a scangauge and it gives a digital readout and they are both fine.

I wouldn't sweat it unless your battery is going dead.