Ford Explorer wandering temp guage issue

Have a 95 Ford Explorer XLT with 4.0 V-6. Several months ago had the temp guage needle wandering up and down while driving. I changed the thermostat and seemed to fix it until yesterday when I noticed it doing it again. No leaking or noises anywhere and no overheating issues. 145000 miles on car and original water pump. The guage seems to creep up to normal temp when idling at a stop. Then when you accelerate from the light can see needle slowly creep down a quarter inch on the coolant temp guage. No operational problems. Car runs fine. Do I have another bad thermostat? Should I ignore it for now? Car warms up normally when cold in the morning and the temp guage doesnt start wandering until have driven several miles.