Intermittent electrical issue

My 2010 Camry 3.5 v6 has been experiencing
intermittent issues. While driving the check engine
light will come on sometimes. Sometimes when I
go to unlock the car with the keypad it barely
makes a noise, then I get in the car and try to start
it and the car just makes a click and all the dash
lights flicker and the car wont start. I turn the car
on the lights will continue to flicker then eventually
come and then the car will start. This doesn't
happen all the time. But it has been going on for
the last 3 months. I have checked the alternator
and connectors and battery please help