Water is probably leaking slowly back into the well due to the check valve leaking. The check valves are usually at the bottom of the well pipe.

Thanks Bob. I hope it's not that. I wonder if they have to lift out the pump to replace a check valve, if they have to chlorinate the system again? I hope that. That's such a pain. I found a really good You Tube on troubleshooting the system, and he mentioned checking the pressure switch to make sure that the contacts aren't fouled up. Would that be a hard thing for a non-fix-it person to check out? Of course, the power would be off. Any ideas about this and cleaning the contacts? Can we take the cover off with the power on, and then turn the water on and watch the contacts in action? Or is it dangerous to even take the cover off with the power on? I know it's scary to give info to nonprofessionals, but we're super careful about electricity.

Oh....and also the You Tube guy said sometimes the small pipe/tube to the switch can get filled with gunk and can't send the right message. How would you clean that tube out? I'm assuming you'd have to take off the switch and run a small brush down there?

If DH let air out of the tank, he needs to replace it. A bicycle pump will do. He needs to get it back up to 35psi.

There can be a check valve at the bottom (usually) and perhaps another at the top or near the tank (input side). Depends.

This is pretty simple. If the pump runs several times during the day without ANY water being used, there is a leak somewhere. It could be a toilet flapper, it could be a faucet dripping steady, and it could be the check valve leaking. But there is a leak somewhere.
If the pump runs often when a small amount of water is being used, that indicates a pressure problem, such as not enough air in the tank, a ruptured pressure tank bladder, or a problem with the pressure switch.
Let’s first determine which of these the problem is.

BobH is correct:

If the pump is running, there is water being used or the check valve is leaking. If it switches on and off quickly, then the pressure tank is waterlogged.

The first places I would look are toilets and any obviously dripping faucet.

If you can shut off the water to the house shortly after the pressure tank, you should be able to isolate if it is a leak at a point of use -- or if it is the check valve (if the pump runs while the water is off to the house it's probably the check valve).

You can put a check valve in above ground before it goes down into the well if there isn't one already - as Weedmiester noted.

Thanks everyone. I have checked every toilet and shower/tub. I did find the tiniest amount of water occasionally dripping from a tub faucet. I put a container under that faucet and it only showed about 5cc of water in 24 hours. I can't imagine that would cause the pump to come on a couple times a day. It just came on as I'm typing this and it ran about 30 seconds. DH checked our large crawl space and saw absolutely no leaks/standing water. The pump doesn't cycle quickly. I wish I could be there when it does this, and I could see how low the pressure is when the pump comes on. I'll pay attention to if the tank still holds at 35 psi. If not, we'll add some air.

If it was a toilet issues, we'd occasionally hear the toilet running, right? Never hear that.

I don't believe we have a check valve by the pressure tank. Could it be what I mentioned above, that the pressure switch has gotten funky?

Our water softener doesn't regenerate on it's own these days, so we do that manually, and know when to expect the pump to cycle because of that.

We have water hydrants out by the barn and the wood shed. I suppose the lines to there could be leaking, right? But since they are so far down, we probably wouldn't know it (no surface standing water). Oh....that gives me an idea. I can shut those off in the basement. If the extra pump stuff goes away, then we'll know it's that, right?

If we can't figure this out, it's plumber time. I don't want to wear out our well pump.

Sorry for my ignorance about these things. I appreciate your help!

It is probably not the pressure switch. If that gets funky (bad contacts) it usually doesn't turn on.

Isolate the problem the way I mentioned. Turn off a main valve where the water leaves the pressure tank so that there is no water going to the hydrants or the house. See if the pressure drops and the pump kicks on.

If it does, the problem is a check valve - and you can install one on the inlet side of the pressure tank.

thanks Jake. Now I understand better what What you said earlier. I will do that test and see what happens. Thanks!