Minecraft freezing on startup

I start up the game, and it goes past the Mojang screen and all then, then freezes at a really low resolution on the title screen. It isn't just being slow, I left the game open for an hour once and came back to it still frozen. For some reason it sometimes gets fixed if I leave the launcher log open. In the log, there are no abnormal errors or warnings other than saying my WIP resource packs are incomplete. The only error is the game crashing. Also, sometimes it runs if I restart my computer and repeatedly run the game, but that's probably random chance.