The blank screen is a warning that all is not well.
It is probably not worth paying someone to look at it. The Tab S2 has been around for 7 years now .. I bought one and have had it from new. Once in a while I also get the blank screen. If it doesn't correct itself within a few seconds I press the power button along with the volume down for about a minute, then restart it.
Personally I back my phone up, but I have never backed my tablet up and save nothing at all on it. I don't hesitate to do a factory reset to keep it running at top speed.
The Tab S2 is a great tablet, as I'm sure you already know, but the equivalent replacement is close to £700.
When it really annoys me I will bite the bullet and replace it. In the mean time I will carry on using it. It may well be time to start checking out the best price for a replacement.