hello if in doubt get checked for you and baby.
probably just practice braxton hicks as with your second baby you should know the signs of true labour.
could also be baby lying on a nerve which is sending signals all over the place.
At 36 wks my daughter experienced this but was her first baby and she actually went a week late.
Sending you the best of luck for you and your little treasure when he/she is finally here in few weeks.
I adore being a first time grandmother and she is now 11 months not long till first birthday.