What word describes the feeling of "shocked by some great things and humbled and overwhelming" ?
I vaguely remember a word which sounds like "contaminated" .
For example, one can say " I am "contaminated" by the great mother nature."
I think I have what you're looking for: "intimidated"
frightened or nervous because you are not confident in a situation: Older people can feel very intimidated by computers.
If you were humbled by great things, such as nature, you were awed. Lexico has
awe
VERBInspire with awe.
they were both awed by the vastness of the forest
If you were also shocked, then you were overawed. Lexico has
overawe
VERBImpress (someone) so much that they are silent or inhibited.
the eleven-year-old was overawed by the atmosphere
So
I am overawed by the great Mother Nature.
It does not begin with 'c' though.
I don't know what word you've forgotten, but the meaning might be summed up in the phrase "bowled over"; since that is a bit informal, here are some search results for synonyms of it:
Merriam-Webster "bowled over"
amazed, astonished, astounded, awestruck (also awestricken), dumbfounded (also dumfounded), dumbstruck, flabbergasted, shocked, stunned, stupefied, thunderstruck
From "wordhippo", "Confounded with surprise or wonder", floored, gobsmacked, speechless, staggered
The only one that starts with "c" is "confounded", which more often has a negative sense.
Another "c" word is "captivated"; that might fit as well.