Arduino+esp8266 restarts after random amount of time

Hello, I just noticed that my arduino restarts after some time, I think that it is caused by network. When HW goes offline(network down, packet loss) arduino just resets. That wouldn’t be a problem in most applications, but I use it to control LED on aquarium, thus it doesn’t look very good when the lights suddenly cut off and start fading from beginning. It is possible to turn it off(so it doesnt restart), or it is some kind of bug?

Oh nevermind. I just figuret out, that this is PSU problem.