6 months and vomiting...any ideas?

Hey ladies! This is the second night in a row that my 6 month old has thrown up.  It's  quite a bit too.  It leaves her soaked and last night she continued to throw up a little about 3 times after I brought her to my room.  I just got her and she was soaked again and hasn't vomited again yet.  She was fine during the day so I thought it was gone whatever was wrong with her.  Now since she's woken up again in vomit I'm worried and I am taken her to her pedi in the morning.  I'm just wondering if anyone would have any idea what it could be? Virus maybe?  It's just weird that it's only at night...