Is there an idiom for one who when faces problems or obstacles tries to forget them instead of solving them ?
Bury your head in the sand can be used to convey the meaning you are suggesting:
to refuse to think about an unpleasant situation, hoping that it will improve so that you will not have to deal with it
- Parents said bullying was being ignored, and accused the headmaster of burying his head in the sand.
(Alludes to an ostrich, which is believed incorrectly to hide its head in a hole in the ground when it sees danger)
(Cambridge Idioms Dictionary)