2009 Toyota RAV4 - I suspect the phone charger

I use a charger for my iPhone or GPS which plugs into the cigarette lighter. Can that device if it’s gone bad affect my starter or otherwise the electrical system? Car sometimes won’t start.

It should not affect your car.
Having said that, if you are charging your phone when the car is not running it could possibly run down the car battery enough to prevent it starting. Your car battery may be weak.

If a phone could draw that much energy from a car battery perhaps one day we will be able to jump start a car with a telephone.

The power outlets in Toyota vehicles are not powered when the ignition is off.

The phrase “sometimes won’t start” doesn’t give us much information. What happens when it doesn’t start?

Silence when you turn the key?

A click when you turn the key?

Slow cranking ?

Normal cranking?

Fast high pitched cranking?

Sputters and stalls?

Fortunately my F150 has power to the power outlets when the engine is off, that’s how I charged my phone when we lost household power for 8 days after a hurricane.
There was another thread several months ago where the poster was drawing enough power charging devices to run down their vehicles’ battery.

Having the ignition on draws about 10 amps, the phone was insignificant in his case.

True in my case, no problem starting the truck after charging my phone all night.
My ignition is only on when the motor is running.