I'm just posting so that if someone else comes across this same situation you'll have an idea of what could be an issue.

We got our '21 ES350 less than two weeks ago. The car has been starting perfectly normal this whole time. Yesterday, my wife drove the car to work and back home as normal. I decided to pull it out of the garage and give it a bath before the weekend. Thing is, it wouldn't start. All the lights came on and messages like "press brake and push start" but it just wouldn't start. I decided to try my wife's keys in case my fob was the issue, still now go. By this time Lexus dealer had already closed. I figured, the battery is almost 3 years old now and that was probably the problem since they don't make them like they used to. I was planning on having to go buy a new battery. I put a charger on the car and it was registering 10v so the battery was definitely way to low to start. It took about 4 hours to get the battery back into full charge and then I confirmed it would actually start now. I decided to search and see what kind of warranty is on the battery since my car is L Certified with a Lexus warranty for the next 3 years. I found where it said the OEM battery was warrantied for 4 years or 50k miles which means it should still be covered for me. Took it to the dealer this morning and this was the diagnosis.

The car's computer was constantly staying in live mode and was never turning off even when the car was shut off, which ultimately drained the battery. They said there was a software update to address this, so, I'm assuming it's a known issue. They updated my car, charged the battery, gave it a nice wash, and sent me on my way.

So, if your car just starts draining your battery, you might want to see if there is a software update that needs to be applied.