I'm not sure why this would happen, and I'm not sure the temperature (unless the wall itself is really really cold!) would make a substantial difference.
But if it's not able to get a picture, I would definitely suggest a service call to get the unit inspected and repaired.
I have an LN-S4041D. After a particularly cold night (TV is near outer wall of home, yet temp in room probably not below 60 degrees overnight) it occasionally will have sound yet no picture. Typically occurs in the morning or when first turned on. After awhile it will stay on, picture is great. I left it on for a couple of days straight, no problems till another cold night and when I got up, the picture again was off, yet sound OK. Once again, after waiting awhile and trying repeatedly, it will stay on. Don't know if the cold night has anything to do with it, yet loose connection worsened by cold temp comes to mind. Or, could this be inverter board, or lcd controller or what?