FPS Changes after leave game or next day

Hello. I have intel i5-9600KF and Nvidia GTX 3070Ti. when i play BF redsec first time. i get low fps like 45-60 and i try some nvidia control panel settings and some windows settings. Then i try to play again my fps is getting better and play very smooth couple of hours with 2k Res full Low settings and DLSS Quality. Next day when i launch game again my fps drop like 45-60 again i try to lower my settings but nothing change. i try like 1080p res and more lower settings but nothing change. i feel like there is a something capped my potential fps and game smoothnes. Then i try same setting like yesterday and couple of pc restarts then somehow i manage play like higher fps with smooth gameplay again with 2k resolution. Then play couple of hours again nicely. The next day, when I happily returned to the game for a new session, even though I hadn’t changed anything, it went back to that low FPS and unsmooth state again. After that, no matter what I did, I could never reach the level of performance I had experienced those two times. Could you help me with this issue?