Is it normal that in 4s sim lasts longer to be recognized?

In my iphone 4 when i started the phone, after entering the code, it asked me inmediately for the sim PIN, now it takes about 5-10 secs, or longer to ask me for the PIN CODE. While the phone shows searching. Apart from this, the phone and signal it's excelent. But i don't know if this is an issue of iOS 5.0.1 or it's some hardware issue. What's your experience?