FPS PROBLEM DESTINY 2

Basically i was playing Destiny 2 and was having real fun. After a while i noticed my fps went under 60 fps. First i was like "It will probably go back up :)" But no no no it just stayed under 60. I restarted the game and it fixed it. Then later it happend again and again and again.. i freaking triggered and cant play the game without worrying about my fps dropping and not going back up to 60.

SPECS : 1070, I5-6400, 16 ram, 256 ssd, 1tb HDD.