Server Crash

[15:48:12] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.OutOfMemoryError: unable to create new native thread
	at java.lang.Thread.start0(Native Method) ~[?:1.8.0_66]
	at java.lang.Thread.start(Thread.java:714) ~[?:1.8.0_66]
	at java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:950) ~[?:1.8.0_66]
	at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1368) ~[?:1.8.0_66]
	at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:367) ~[minecraft_server.jar:git-Spigot-3d850ec-809c399]
	at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:739) ~[minecraft_server.jar:git-Spigot-3d850ec-809c399]
	at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) ~[minecraft_server.jar:git-Spigot-3d850ec-809c399]
	at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) ~[minecraft_server.jar:git-Spigot-3d850ec-809c399]
	at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [minecraft_server.jar:git-Spigot-3d850ec-809c399]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_66]