Which one would be correct: I haven't moved in awhile or for awhile when referring to traffic- i need a clearer explanation for- for awhile and in awhile
The correct form should be "for a while".
"In a while" is used to point out one or more points of time in a given period (when).
I played cards once in a while (, but did it more often before).
In a while I'll leave this place.
First example: Referring to how often I did it in the period of time.
Second example: Referring to the point in time I'll leave in the period.
"For a while" refers to the period of time as a whole (how long).
I slept for a while.
I was unable to sleep for a while.
In this examples the thing you do or do not does not change in the period of time.
An example that shows the two meanings:
I will play soccer for a while. (how long)
I will play soccer in a while. (when)
You should also understand the difference between a while (with space) and awhile. This post does a good job of explaining but I will summarize.
A while is a noun phrase meaning 'a period or interval of time'.
Awhile, is an adverb meaning 'for a short time or period'.
The adverb 'awhile' cannot follow a preposition, but you can re-work a sentence to use either properly and not have the meaning changed drastically.
I haven't moved for a while - means you have been stationary for a period of time.
I have been here awhile - means you have been stationary here for a period of time.
If your question was just about in vs for in the noun usage, Daniel did a good job explaining that above.
These have the same meaning to me, but that is my opinion; I don't have a reference to point you to.
However, I will note that "awhile" should be two words: "haven't moved in a while" or "haven't moved for a while." I hope this helps!
See also this related question: "In a while" vs. "for a while"