The answer depends on the frequency, and to some extent on the degree of damping of the system. Assuming you are talking about a lightly damped oscillator (without damping the amplitude continues to grow so there would be no steady state), we have to look at the phase as a function of frequency.

The math is worked out on this website (or frankly, 1000's of others). The phase difference between the driving force $F = A\cos\omega t$ and the response amplitude $x = x_0 \cos(\omega t - \phi)$is given by

$$\phi = \tan^{-1}\frac{\nu\omega}{\omega_0^2-\omega^2}$$

Of course the velocity is the derivative of position, so there is a $\pi/2$ phase shift between position and velocity.

At resonance (when $\omega = \omega_0$), $\phi = -\pi/2$ and the force and velocity are in phase (this is how you get the optimal coupling of power into the oscillator). But at that point there is a phase shift between displacement and force of $\pi/2$.

Note - the acceleration of the mass is due to both the restoring force, and the driving force; you cannot simply equate "the force" with "the driving force" as that ignores the role of the spring (or other restoring force). A system without a spring has a resonant frequency of 0, and then all the above math becomes meaningless.

The answer depends on the frequency, and to some extent on the degree of damping of the system. Assuming you are talking about a lightly damped oscillator (without damping there would be no steady state), we have to look at the phase as a function of frequency.

The math is worked out on this website (or frankly, 1000's of others). The phase difference between the driving force $F = A\cos\omega t$ and the response amplitude $x = x_0 \cos(\omega t - \phi)$is given by

$$\phi = \tan^{-1}\frac{\nu\omega}{\omega_0^2-\omega^2}$$

Of course the velocity is the derivative of position, so there is a $\pi/2$ phase shift between position and velocity.

At resonance (when $\omega = \omega_0$), $\phi = -\pi/2$ and the force and velocity are in phase (this is how you get the optimal coupling of power into the oscillator). But at that point there is a phase shift between displacement and force of $\pi/2$.

Note - the acceleration of the mass is due to both the restoring force, and the driving force; you cannot simply equate "the force" with "the driving force" as that ignores the role of the spring (or other restoring force). A system without a spring has a resonant frequency of 0, and then all the above math becomes meaningless.