Headlights problems of the 2007 Lexus GS350

I also have a headlight that has intermittently not worked. I run my lights on the auto feature. In the last 6 months, I have noted that the left headlight only turns on some of the time. I need to check it, turn the lights off, then back on to get it to work. Happens about 20% of the time and is a safety issue. About 3 years ago, someone followed me into a store and told me that my left headlight was out. When I left and turned the car on, then checked the headlights, they were working. I now realize that this is when it started.