Are vibration sensations baby's movements?

I'm 17 weeks along, and this is my first pregnancy. Today as I was taking a nap I felt this weird vibrating feeling! It was so strong that it woke me up twice. Each time lasted for maybe 7 seconds. It felt like a cell phone was vibrating in my stomach. I've already felt *tiny* little flutters every now and then when I'm *really* still. Are the vibrations the baby's movement? I was reading online that it's the baby's movement, but I wanted to hear if other's have had a similar experience!