iphone keeps saying please insert sim card but there is one in there

[maf2k8]

This just started happening today my iPhone 4 keeps saying there is no sim card inserted if I shut down and restart its fine for awhile then it happens again. I reseated the sim and still same ssue what is the problem

 

[shagthedrummer]

restart the phone. problem solved.

 

[Simgar988]

My friend is having the same problem and he is at the AT&T store added speak. He got a new sim and it still didn't work