It’s normal. Just like adults, some days you just want to lie there and do nothing. As long as there is movements I wouldn’t worry too much. Sometimes they get too active due to the food or drinks you consumed. Eg cold drinks, sweet drinks or even spicy food. Also, they may also react to a certain music played. My baby used to move a lot in the tummy when she hears “Happy birthday/Merry Christmas and Happy by Pharrell” 😂