Fetal movement in ultrasound?

Im 10 weeks 5 days pregnant. at 10 weeks and 1 day pregnant I had a lengthy ultrasound at the hospital and my baby was moving a lot! it moved its arms and legs, its head, everything! but today my OBGYN did a quick ultrasound on the portable ultrasound machine just to check babys heart...and the heartbeat was normal but this time i didnt see the baby move at all. Why is that :( is it because it was a crappier ultrasound machine? or the baby was sleeping? It was just kinda frightening to me that I just saw it moving like crazy a few days ago and today it was completely still, but my doctor had no concerns.