Sony trinitron model KV-A2913E chassis AE1C shutdown only once until warm

I am proud as owner of this old TV but nowadays it auto shutdowns itself after around 1 or 2 minutes since I turn on. It does not happen always but when the problem appears I have to switch off and switch on again. Once I switch on, the TV is running again (without stand-by) and I can watch TV without any problems. This problem does not repeat until next day or next two or more days- The only thing is that it happens once. I do not need switch on two times on a row.
It´s a strange and random issue so before open it, I would ask your opinion about what kind of protection is working.
I will several checks like waiting in stand-by (to warm up) before turn on in order to find out the cause.
Thank you for reading me.