How often do people use cheats?

I've been playing for 1 year now I'm on 1530 elo, and sometimes I've got the feeling that my opponent is doing weird things or playing at a level he's not supposed to play.

In fact, some times I just get random messages "your elo has been adjustated because ... +8 elo" because someone cheated.

Just played a dude that after lose a pawn on opening started to do weird things. First, every move I make he goes into "automatic resign in 59... 58... 57..." Etc, then he returns after 10-15 secs and do a move.

After 3-5 moves I've noticed his "random" moves just led to a situation where I was in a clear disadvantage.

What's this message? Why do people goes into automatic resign then returns over and over again? Is because they are checking a third party app to do the move?