It sounds like what I would get trying to play on a board using integrated graphics for a while.
Looking up your motherboard, it does look as if there is integrated graphics.
You have no discrete graphics card, correct?
Could you at one time play these games without the 20-25 second lag periods?
Often with integrated graphics in my experience, after a while and overtime even with the same games that can play average without these lag periods, it will start to wear down. Performance over a year or two can be the introduction to these sudden pauses as the graphics attempts to keep up.
The first thing you want to take inspection of is the dust in your case, in the heatsink, cpu fan, any other fans in the case, etc. Heat can be a major cause of things slowing down. If there looks like there is "matting" in the fans or the heatsink and cpu fan, then there is a major issue with is fortunately easy to take care of.