The volume will increase.
Assuming that the pressure of the gas is kept constant, more forceful collisions between the molecules of gas and the walls of the container will cause the volume to increase.
The only way to produce produce more forceful collisions between the gas molecules and the walls of the container, provided that pressure and number of moles of gas are constant, is to increase the temperature of the gas.
When these conditions are met, temperature and volume have a direct relationship described by Charles' Law.
When temperature increases, volume will increase as well, and when temperature decreases, volume will decrease as well.
As you know, temperature is a measure of the average kinetic energy of the gas molecules.
When you increase the temperature of the gas, you're essentially increasing the average kinetic speed of the molecules. As a result, the collisions with the walls of the container will become more forceful and more frequent.
Because these molecules will push against the walls of the container with more force, the volume will increase.
SIDE NOTE. If you were to increase the temperature of a gas trapped in a rigid container, the pressure of the gas will increase.
This happens because of the aforementioned reasons - more powerful and more frequent collisions between the molecules and the walls of the now rigid container.
This is known as Gay Lussac's Law, which states that pressure and temperature have a direct relationship when volume and number of moles of gas are kept constant.