Play from Now not Start

There's an option in the track view to start playback at Now position. Perhaps you inadvertently changed this setting?

In the Track Pane, there is a tab labeled Options, and within that drop-down is an option that Sonar has set to a default of being checked, with that option being: On Stop, Rewind to Now Marker.
 
With it checked, when you stop the transport, Sonar will indeed rewind to wherever the Now Marker was last 'set'.  When I am recording or playing back, this is how I almost always leave it set.
 
When that option is NOT checked, Sonar will simply leave the project positioned at the moment that the transport is stopped.
 
I run with the option not checked when I am working through a track with an intent to edit, so that when I hear a clinker (something needing change), when I stop transport it leaves me very close to the spot where the edit is needed.
 
Another way of approaching the above is to leave the default setting of that option being checked - so that when the transport is STOPPED, Sonar rewinds to Now Marker's position of last being set, but when the transport is instead PAUSED, Sonar will leave itself positioned right at its current location then PAUSE was pressed.
 
So, it's up to the user to determine how to control Sonar's positioning behavior - I suggest trying the above choices a few times, to determine which approach you like better, and then consistently use that approach.
 
Bob Bone
 

robert_e_bone, thanks for the hints. I tend to stick with not returning when I stop, as I use the spacebar to do all my starting and stopping
 
Cactus Music, it may be an inadvertent hit of Ctrl-W, maybe instead if a Shft (?) that set it to returning to now. I'll remember that.