2008 Volvo S40

DSTC "Dynamic Stability Traction Control"
You should still be under factory warranty to have them diagnose and fix the problem. Without doing a readout of the car at this point it would be impossible to try and give you advise. But if you have a wheel alignment that is off causing the steering wheel to be off centered, the traction control will slow you down and can be very anoying. I hope this information helps you understand a little bit of how DSTC works and the importance of correct wheel alignment.

STC
Stability and traction control system consisting of two parts:

Traction control. Traction control (TC) is a traction control system which is integrated in the ABS-system. The traction control system distributes the driven power between the wheels so that the wheel with the best road traction receives the greatest amount of driven power. The system is mainly designed to assist when moving off on slippery surfaces at speeds up to approximately 60 km/h. Traction control has only a very limited effect at speeds above 60 km/h. To prevent damage to the brake calipers and discs, traction control is disabled if the brake discs become too hot. The traction control function is always engaged when the ignition is switched on. This function cannot be disabled manually.
Stability control. The stability control (SC) system is integrated with the ABS system. It stabilizes the vehicle in the event of wheel spin. The brake control module (BCM) transmits a signal to the engine control module (ECM) to reduce engine torque until the slipping wheel(s) has/have stopped spinning. The stability function is always engaged when the ignition is switched on. Stability control can be engaged and disengaged manually using a switch on the tunnel console.
DSTC
DSTC (Dynamic Stability and Traction control) - a dynamic stability and traction control system which is integrated into the STC (stability and traction control) system. The DSTC (Dynamic stability and traction control) system consists of the following:

Traction Control - This function is described above under STC - Traction control above.
Stability Control - This function is described above under STC - Stability control above.
AYC (Active Yaw Control). The system is based upon a number of sensors which sense the driver's steering movements (steering wheel angle) and the directional, both straight and lateral, movement of the car. This information is used to correct the car in the event of oversteer or understeer.
DSTC is always engaged when the ignition is switched on. Stability control can be engaged and disengaged manually using a switch on the tunnel console. The same switch can be used to set the sensitivity of active yaw control (AYC). It can be either in normal mode or in wide slip mode.

So if your alignment is incorrect and steering wheel is off centered, that information is sent to the brake control module and looks and compares at your speed and steering wheel angle position. From there it will think you are oversteering or understeering and will try to correct the situation causing a reduction in torque and slowing you down. If alignment is correct then you really should take it in to Volvo for proper diagnosis and repair.