92-95 Civic owners -a Q

[Nerds laugh at me]

I notice that my gas guage barely moves untill I hit around 100 miles on the odometer. It drops almost a good 1/4 inch or so the next time that the car is started, but not really all that drastically when I drive a constant trip of over 100 miles. It only seems to just plummet when I take short trips and restart the car every 20 or so miles. ( And I know that starting the car does not burn up that much fuel )
What is causing this ?
Is the float getting hung up on something ?