Macbook Pro is running hot after a restart?

I restarted my Macbook Pro over the weekend for the first time since classes started back up in January. I do a lot of Safari, with multiple windows open and multiple tabs in those windows, as well as play a little Minecraft and do some light Photoshop work. Before I restarted my laptop it would only rev up the fans when I was playing Minecraft or doing photo editing while I was watching a youtube video, other than that it would stay fairly warm but never enough to kick on the extra fans. But now after the restart over the weekend I find it turning on the fans even when I'm just doing some research on Safari, not even streaming a youtube video or anything. So the fans are quick to come on now, but I also hear a faint noise of a fan or something rotating, its a quiet hum that I can only hear between songs or when the TV is muted. I can't seem to find any consistency with the hum. I picked my laptop up this morning and it was humming but now as I type this with 3 Safari windows and 15-20 total tabs open it is quiet. Any ideas what might be causing this? Its a late 2011 Macbook Pro with 16GB RAM and a 2 year old Logic Board (had to be replaced, but that was the only problem). I also had my fans break or something before and they replaced them but this doesn't seem to be the same issue, before they weren't coming on at all and now they are coming on when they shouldn't be. Any help would be greatly appreciated.