This has happend to me every so often, id agree with greens...kinda the dejavu feeling but a bit different. I think its the aspect that humans can wonder "why" they are here etc and look deeper into things, where as animals are more based on instinct, as in they dont really care why they are alive or here, just eat, sleep, reproduce. I dont really think its a problem or a result of anything direct. Sometimes, you just "wonder" i guess is the best way i can put it.