Whilst I can't really help you resolve your problem you certainly are not alone with it. This happened to me 3 times in my 2009 RX450H SE-I. It (for me) always happened when I came to a stop, usually at a junction. I'd restart the car after a few seconds and it would start again but then all of the lights/warnings you mention started coming on one after the other. I did have a few more warnings than you mention, Pre Crash System fail, Brake System Fail, ABS Fail.
Lexus checked the errors and said the only error that was there was one that said 'Communication with hybrid system lost'. They reset it and could not get it to happen again so gave me the car back. It happened a few weeks later, took it back in and this time they said the ABS sensor at the back was faulty and needed replacing. I asked why all the other warnings came on and they said that if the ABS sensor goes pear-shaped then it has a knock on effect on the other systems.
I wasn't too convinced but I also had problems with battery drain, it would be flat in 3 days on the driveway. Charge it up fully and it would be flat again within 3 days. Went back to Lexus and they had it 3 days, could not find a fault but the mechanics noticed that whilst my car was on the ramp and they were eating lunch they saw my car turn it's headlights on, on its own then turn them off after a few minutes. When I got the car back I turned off the auto lights and the battery stayed charged.
Never got to the bottom of the cutting out/warnings as I stopped trusting the car so PX'd it for a 2017 RX450H which I picked up yesterday.