de Vaan writes in his Latin etymological dictionary, s.v. dormio:
The PIE roots *drem- and *dreh*dreH- both have two meanings: ‘run’ and ‘sleep’.
For example Latin dormire ‘to sleep’ and Greek dramein ‘to run’ (aorist stem), but darthanein ‘to fall asleep’. But given the semantic distance, it is perhaps better to regard these as two sets of IE homonyms.