4 month old won’t eat

Since 10:30 AM. it’s now 7PM. I’ve checked him head to toe multiple times. For hair wrapped around anything. No cuts no bruises. Nothing. Even gave a bath. He’s a very happy baby most of the time.

He got shots on Monday, had a fever yesterday but was eating. No fever today. Slightly fussy but sleepy. No teeth yet but drooling so i’m sure it will happen soon.

Should i be concerned or does this happen sometimes?