Volvo: Goes into Trac Mode automatically, volvo 850 glt, rear brakes

Question
Hi, In the winter when it is cold our 1996 Volvo 850 GLT, not turbo, once in awhile the TRAC LIGHT goes on automatically and when I step on the gas the car goes very slow until I drive it a bit of a distance than it drives normal. I am having new rear brakes and new rotors put on this week.
Is this a major engine issue and very costly to fix?  We where going to trade this in for a newer auto, but due to the economy, we are retired living on a fixed income and have lost half of our savings, decided to put the purchase on the back burner.  Do you recommend us having this fixed?

Can you answer this asap as we need to know what to do and if we should purchase a newer vehicle today.  Thanks,   Robert  

Answer
Robert,
Your problem sonuds a bit complex. Maybe more that one probelm. Tracs is traction comtrol. I see no reason that the tracion control would slow the car down. My guess with driving and reading fault code would be something in the trans. Take the car to a shop that knows the Volvo show them the faults, so they see what is going on.
If it is the trans is at fault it will be costly.