Hey guys am in need of help, I bought a 1997 klx300 earlier this year in June and has been running great until now.

when I start up the bike it runs fine for about 30 seconds and then the bike starts to pull itself foward when in neutral? I have no clue what it could be. Also, the bike idles fine but will randomly die. If you need more info to troubleshoot just ask. Thanks in advance.