Q: ipad doing quite strange things in Safari

Hi! Today i was in a website watching tv series online,i clicked on a link to watch the chapter, the screen became black and the apple logo appeared and you can hear the sound that let you know that the device is locked. After that then locked screen appears and ask for the code to unlock the device. I go to Safari and I can watch the chapter that i was going to watch before. This happened to me already four times. Quite strange!