The drum turns and the timer counts down, but nothing warms up. That combination rules out half the machine straight away — here is what is left.
Common dryer problems
All dryer guides
Dryer Runs but Never Gets Hot: Narrowing It Down
Dryer Squealing or Grinding: What the Noise Tells You
Drum rollers, the idler pulley and worn bearings each make a different sound. What you hear, and when, narrows it down before anything is opened up.
Why Your Dryer Needs Two Cycles to Dry One Load
Heat is present, clothes still come out damp, everything takes twice as long. That points at moisture leaving the machine, not at the heater itself.
Dryer Will Not Start: Splitting the Problem in Two
Whether the control panel lights up decides which half of the machine to investigate. That single observation eliminates most of the possibilities.