Loud223

I have a weird issue with the AM radio. If the car sits overnight or a couple of days the AM radio station is scrambled ( like its just off by little) If I switch to FM, FM is fine, SAT is fine, when I go back to AM it clears up. If I go to work and run some errands it doesn't do it. It only does this after setting at least over night, but it's not consistent. Sometimes it does it sometimes it doesn't.
Any thoughts?