I wanted to say "I'm going to take a nap for a while" and looked for the phrase "(for) a while" in Chinese and came across these 5 : 一会，一下，一时，一时半会，片刻。
Could you please tell me the difference between those five?
Will there be any difference if I say :
And last, does adding "儿" to 一会/一下 change the meaning?
Thank you in advance!!!
(Ps : I'm a beginner in Chinese. I'm sorry if my question sounds silly or something. Also, it'd be very helpful if you could provide some examples while explaining things so I can understand better).