I could not find any relevant information on the internet except the PIE had the root dre- for sleep (Vasmer)
First, Russian дремать 'sleep' (дрёма 'a nap' is derived from this verb) and Latin dormio 'sleep' (> dormito 'feel sleepy') are cognate (Горяев; Trautmann; Преображенский; Berneker; Младенов; Boisacq; Vasmer; Machek; Slawski; Pokorny; Buck; etc.). Where did you find Latin "dormatio"?
Second, English dream has no plausible reconstruction even on Proto-Germanic level, ref. at least Oxford Dictionary of English. There are semantic reasons why etymologists are not eager to postulate a protoform, more on this read, for example, here: https://www.etymonline.com/search?q=dream.
Since the aforesaid, dream is unlikely to be cognate for Russian дрёма and Latin dormio though the latter obviously are.
Some Russian scholars (Шанский et al) claim that German Traum (of which English dream is a cognate) shares the same root with Russian дремать. Nevertheless, this seems doubtful in the absence of special comments on the English etymology (see above).
Trustworthy Etymological Dictionary of Slavic Languages does not mention any German cognates: