Kenmore 500 won't heat after initial firing

Hi all - hoping you can help me diagnose my dryer issue. After initial ignition, flame stays on and dryer heats for maybe 5 minutes. After dryer reaches a reasonable temp and flame goes out, the coils glow for maybe 60-90 seconds but won't ignite and the dryer runs on just air.

Anyone have ideas or know what/how else I can test?

Thanks much,
Karyn