my interior lights randomly go on

check the switches in the door if they are right check ground wire on the switches

I have a 2004 Toyota Sienna and I've ran into this issue multiple times and both times it was the sliding door push-button switches that are pushed when the doors close. I have written up a complete tutorial for trouble-shooting and replacing these switches here: http://www.shareyourrepair.com/2013/02/how-to-fix-sienna-dome- lights-randomly.html

I have toyota sienna SE 2015, and i don't understand why it doesn't come with door welcome light, it just have a red reflector, can I install lights on it?