Hello. My jet pump goes on without using the water. It happened 3x last night. Do you have any ideas? Thanks for your help.

Got to be a leak somewhere. Is there a shut off valve between the pressure tank and the house? If so, turn the house off and see if the problem continues. If it continues, then the problem is in the well. However, could be as simple as a leaking flapper valve on a toilet.

I would agree there probably is something leaking in the house, possibly toilet. You may also have a bed check valve at the pump
RJ

Most likely Your leak will be found on the pressure side of the system.
If your pump has a pressure gage then follow the advice
Given above. Let's see if I can make it easier for you.
Starting at the pump, shut the water off at the house and let the pump run until it shuts off, Note the pressure reading.
Wait one hour and check the gage, Did the pressure drop?
If yes the leak's in the line from the pump to the house IF no then the leaks in the house or it's a long shot but you could have a faulty check valve on the suction side.
If the gage held the reading then your problem is in your house. Do you have a sprinkler system that feeds from the pump?
Open the house and pressure up the house. Any dripping faucets? The most likely will be the toilets. Take your finger and run it around the flat part of the flapper, If you feel a wavy edge, replace it to double check a leaky toilet tank at bedtime put some food coloring in the tankDo not flush until morning If you see color in the bowel replace the flapper. Other culprits could be a water softener or a house filter if you have one. Hope this helps and let me know how you came out. Cheers, nTom