Why does iPhone 4 show apple logo?

I was using my iPhone. An app and then switched to the safari internet app. Then the apple logo appeared (white and was bright) then logo went away. Went to lock screen. Then went to menu with apps. Home screen. Why did it restart or do the action?
I did not push power button top.

I have iPhone 4 black.

My iPod 5 does this, I think it's just a glitch in the system. If you're really bothered by it- call apple and see if your device is under a warranty.

It's a firmware bug and a reset should solve the problem.

Springboard crashed

It means the phone crashed and rebooted.