Using the new 22.08 update. Sometime, not always, when I click the mouse pointer to any bar's starting point in the time ruler (e.g. for selecting bars), Sonar's engine starts running the song project in the same way I had clicked the play button. Never happened before.

Hi. I have not seen this behaviour. 
This is just a guess, but do you have a wireless mouse? If so, have you tried switching batteries? Or tried another mouse? It sounds to me like you mouse might be sending double clicks, when there should be a single click.
Could be worth checking.
All the best.

I think Zargg71 is on to something. What's described will happen if you double-click in the timeline instead of just click (it will also happen if Play is already engaged, but that doesn't sound like the case here). This is actually one of my favorite "shortcut"-type features.