1. Verify your filter is not clogged.

2. Verify the vent hose and ducting is clear.

3. Verify your timer is functioning properly: Turn to any timed setting, start dryer, and check in a few minutes to see if it advanced. If it did not, replace the timer. The timer is a mechanical device and they do wear out.

4. If timer is advancing rotate to a STOP or OFF position to turn off power, disconnect plug from wall, remove back panel(s), check continuity of heater element (electric dryer), all thermal switches, thermal fuse. If any have no continuity at room temperature, replace.

5. Additionally, if necessary, the timer terminals can be checked, but will require the use of a wiring schematic and switch continuity chart to tell you which timer circuits need to be open or closed based on the timer position. The info may be taped inside your dryer. If not, attempt to obtain a copy for your model from the manufacturer, or from many web sites, including this one.

Good luck and keep checking back.

FYI, when posting be sure to include your dryer type (gas or electric), Make and Model #.

Those with more experience than I will appreciate the info, and you'll get a more detailed response.