adverb, adverb taking the 'to' particle
indiscriminately; recklessly; excessively
Adverbial use, often as やたらに or やたらと. It can mean doing something without proper judgment or doing/being something to an excessive degree.
やたらに人を信用しないほうがいい。
It is better not to trust people indiscriminately.
今日はやたら暑い。
It is unusually hot today.
na-adjective
indiscriminate; random; excessive
Na-adjective use, as in やたらな. It describes something careless, random, unfounded, or excessive.
やたらなことを言うと、あとで困るよ。
If you say careless things, you will have trouble later.
やたらな約束はしないほうがいい。
You should not make promises recklessly.