On inline booster pump on city water, kicking on everytime something is activated. Also incoming psi is at 35

depending on the control unit in place
( pressurized diaphragm or integrated pressure controller ), that is where your problem is
if diaphragm , check that you still have a air pressure on the diaphragm for control ( normally set at 45 psi max to 35 psi minimum switching
If integrated , replace the unit as it is malfunctioning

something wrong here. your incoming pressure is 4 psi ( tank pressure to the pump and you use a pump to boost pressure to a maximum of 65 psi at which point the pump is shut off ( all taps close off)
yet with no pumps running the pressure goes up to 100 psi
Find where you are getting pressure in that is making the pump leak
if you have 100 psi to the pump when it is turned off, then it would not be turning on ( power on) as the shut off pressure is set at 65 psi and the line pressure is 100 psi

proper way is to install a water pressure regulator and due to potability reasons it needs to be brass ,bronze, stainless steel, or CPVC plastic , (no steel or cast metal) of course the less high tech way is to plumb a valve from pump outlet back to its inlet and adjust valve to max pressure setting you want at max demand , I don't recommend this method as it wont be able to give you a constant pressure regardless of demand as the first method will , Note: some water regulators are a "relieving" type and require special install methods and maybe three lines to it

For a machine without a break-tank (a.k.a. cistern) and booster pump: check the inline debris strainer on the rinse water pipework; check you're not missing any rinse jets; check the inlet valve is fully opening.

For a boosted machine, check the pump impeller isn't disintegrating; check that the flexible hoses to the booster pump aren't collapsing internally.

For both machines: descale if you're in a hard water area.

Is it newly installed or has it been working for a while till you noticed it?

Mine did that. Little known that the Grundfos MQ pump has a small pressure tank on the end. If the pressure is low and the air volume is therefore low, then any tiny loss of water results in pressure drop and pump cycles on. Check the pressure in the tank. This is not well described in the Grundfos service manual.

To pump up the pressure bladder:
1. remove the rear cylindrical cover (swift bash with a fist downwards)
2. unscrew plastic cap on the end (about 2 inches diameter with tapered sides
3. attach pump to schrader valve and pump up (22-25 psi according to service manual)

Reassemble.

Suggest teflon tape to schrader valve stem to try to create a secondary airtight seal.

Grundfos said the problem of on off every few seconds was air in the line. Then

later admitted it was the control unit. After replacing two units in 2 yrs I replaced

it with a standerd pump pressure switch.....Runs fine

Most states only require that the locality only provide you 10 psi at meter and that's just plain wrong because at 10 psi it will not even provide enough pressure to take water to shower head.Most house have about 50 psi you can not have above 70 psi or it will cause a lot of problems you have to install a pressure reducing valve for high pressure for too little of pressure you may have to install a pressure booster pump,which is around 500.00 plus installation.If city not providing enough psi contact pubic works officials tell them if you don't get you more pressure you will install booster system and that will **** their lines dry and cause all the neighborhood to be calling about no water,thats what I did and had engineers and workers provided me with 55 psi at my meter.

You need to bleed off the air. There should be a bleed port on the housing to do this. If that does not solve the pump coming back on, it could be air in the pressure switch.

It depends on the actual valve. The valve that comes standard with the system is designed for typical municipal water pressures of around 35 to 40 psi.

It is easy to replace the valve for one with higher pressure ratings.