Jeff:
Sounds like you’ve got an obstruction in the fill valve. You will have to turn off the water valve below the toilet, or the main valve to the house. open a tap at the sink to remove pressure.
You may be able to dissassemble the existing fill valve on the toilet by removing the screws on the top, and accessing the diaghram valve. With this exposed take a sealer jar, hold it upside down, over the valve, and have someone turn in the water to flush out any obstructions.
You may have to replace with a new fill valve if this doesn’t work.
John Boy