Acer Nitro 5 Black screen issue

It's probably a graphics card issue. 

It's best not to take any action until it completely fails.  Once it fails completely, it'll be easier to identify the problem and make the correct repairs

If you take it for repair now, they might misdiagnose it and potentially damage the laptop further.

In the meantime, connect the laptop to an external monitor. Observe if the blank screen issue occurs on the external monitor as well. This will provide valuable information to the repair technician, helping them to diagnose the problem correctly when you take it in for repair

Do you close the lid to put the laptop into sleep mode? 

I have the same model and I've encountered the issue only once - probably more than a year ago. And at that time I had a lot of applications running, it was charging and Nitrosense was showing CPU temp as over 92 (right now it is 49 - so you get an idea). I thought it was either a memory problem or Graphics card had an issue because of the high temps. I put it into sleep, disconnected charger and after awhile it was normal as usual. I have not encountered it since. My old Dell XPS had a known graphics card issue and it used to do it all the time - so it's probably something to do with the integrated graphics card. 

I thought about taking it to the service center to have the fans cleaned just for better ventilation. But I dont have any issues with the laptop so decided against it since opening it might lead to other problems if the technician screws up.

I have same model of laptop, I bought it on 2019 January and Till 2023 December It had no issues. But From then Some of it's keys have stopped working, No response while pressing it. I changed the Keyboard for Rs 2500 , Now from last week I'm facing the same issue. Any suggestions?