Won't go in gear when started and sometimes won't start

I have a 2013 Cadillac SRX and I drove it all day and then stopped at the grocery store and when I got back in the car, it would not start, but the dash lights came on. Kept getting the message "no key detected" and all dash lights were on, the battery light, ABS, park light and all was on. The key fobs would not do anything, not even lock or unlock the doors. I left it sitting overnight in the parking lot and when I went back the next morning, the car cranked up and went in gear. I drove it home and now it's sitting in my yard. I had replaced the battery and alternator and car worked perfect for a week before having all this trouble. Please help.