I'm looking for a word to describe someone who is so nice they impose on you

well-intentioned collins dictionary

If you say that a person or their actions are well-intentioned, you mean that they intend to be helpful or kind but they are unsuccessful or cause problems!

It depends upon whether or not you want a negative connotation. If you do, then some possibilities might be meddlesome (or meddling), do-gooder, or intrusive. If you do not want a negative connotation, then a single word might not be enough; you might need a fuller description to convey the notion that the person means well but unintentionally crosses the personal boundaries of others.

It may be too forceful a term, but I am reminded ever so strongly of the term 'smother' here.

1.1 Make (someone) feel trapped and oppressed by acting in an overly protective manner towards them.
‘it's time for you to leave the house—she'll smother you if you remain’

Reference:
https://en.oxforddictionaries.com/definition/smother