fluctaution in fps

i have had insane fluctuation in fps...  i have a 4070 super with a 7800x3d so i should get easily 300 since i have a 300hz monitor too... 

normally as you can see in  the vid i get 300 but the last 3 days been so weird it started going to 150/180 and staying there i was so confused and tried about everything. redownlaoded drivers then it worked for a bit at 300fps again and when i turned my pc off/on it went to 150 again it seemed like everytime i did a drastic change to the computer it worked but when i turn it off and on again it becomes a potato... i even hard reset my pc cause i thought this would fix it but infact it did not...