2001 s500 radio shuts off with ignition off ?

[sweetS500]

Quick question. Just had my 2001 S500 for a month or two. Lately it started shutting off the radio when I shut off the engine. So when I start it, I need to power up the radio with the radio power switch. Is that a user option I hit somehow, as it didn't do that until last week or so. It's a BOSE with NAV Command 2.5.