Lag with rtx 2080 ti and 19900k

[Arrons]

sometimes my pc starts to lag for no reason and then when i restart my computer or the game it no longer lags like say for csgo when i hop into a game it starts to lag and then some other times when i hop into a game it doesn't lag this is the same for every game i play forest, minecraft, gta, and even...... roblox. I have called tech support dudes to come over and see the problem and they couldn't find anything they told me it might be that the cooling isn't too good because i have fake windows next to me and a window behind me that opens and its got very little spacing between the back case fan and the wall i am using the thermaltake view 91 and a rtx 2080ti evga ftw3 black with a i9900k and a Corsair H100i Pro so im not really sure whats going on if you guys could help that would be great.

[xAcid9]

When it start lagging, check your RAM usage. I suspect memory leaked. 

[krakkpott]

Check your temps (I recommend HWinfo) & hardware usage (Task Manager).

[Arrons]

I did they were all under 70

 

but i will check the ram usage