It does not indicate a sin or any problem with you, so don’t worry. However, if you want have them be reduced, you can make the following Du’a right before you sleep:

اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الِاحْتِلَامِ وَ مِنْ سُوءِ الْأَحْلَامِ ، وَ أَنْ يَلْعَبَ بِيَ الشَّيْطَانُ فِي الْيَقَظَةِ وَ الْمَنَامِ