A dryer that tumbles without heat is a different problem from one that will not start at all. The motor and controls are fine; the heat source or the thing that cuts it is not. On a Samsung that source depends on whether your dryer is electric or gas, and the first check is the same for both.
Check the airflow first
A clogged vent makes the dryer shut heat off to protect itself, so it feels like no heat. Clean the lint screen, then disconnect the duct at the back and feel for airflow with the dryer running. Weak airflow means the vent needs clearing before anything else is blamed.
Electric dryers
A 240-volt dryer needs both legs of power. If one breaker leg trips or one fuse in the panel has failed, the drum can still turn on the remaining leg while the heater gets nothing. Look at the breaker for the dryer; a partly tripped breaker can look on. If the breaker is fine, a failed heating element or a blown thermal fuse is the next place we look, and a meter is needed to tell them apart.
Gas dryers
A gas dryer needs gas supply, an igniter that glows, and valve coils that open. Confirm the gas shutoff behind the dryer is parallel to the pipe. If you smell gas, stop, leave the room and read our safety guidance on gas smells before touching anything else. A glowing igniter that never lights the burner points to the coils; an igniter that never glows points to the igniter or the sensor.
What cannot be concluded
Long drying times with some warmth are usually airflow. No warmth at all is usually a lost heat source or a tripped safety device. From the damp clothes alone we cannot say which, which is why we measure at the dryer.
Pick a three-hour window on the dryer repair page and we will measure the heat and airflow at your dryer. We work throughout the Houston service area, give you the price in writing ahead of the repair, and warrant our workmanship for 30 days.