Philips 42PFL3605H/12 issue

Hello,
I have a problem with my Philips television, model 42PFL3605H/12. A few months ago, the TV started turning off by itself, but it only happened very rarely, and when I turned it back on, it worked perfectly again. However, for the past month, it only works for 5 minutes before turning off, and even when I turn it back on, it doesn't restart. I consulted various forums, but I'm really a novice at electronics. I took off the back cover to see what was going on, and I don't see any visible problem on the power board. The board is a 715G3812 P02 H20 003U Z-SIDE.
So my question is, is it repairable? If so, is it easy, or is it better to go to a professional repairman? Considering that the TV is relatively old, but I would still prefer to try to repair it rather than throw it away.
Thank you