Hmm well.. Depending on how strong this feeling is.. maybe:
- ' There' s something fishy about him'

(seems like a good one to me

)
- There' s something not quite right about him
- There' s something off about him
- He' s a charlatan
More towards an uneasy feeling:
- He gives me the creeps (when someone gives you a nasty or uneasy feeling) or ' He creeps me out'
- He makes my skin crawl (similar to creeps)
http://idioms.thefreedictionary.com/make+skin+crawl
Perhaps the native English speakers can come up with better ones though.
__________________
"Roam with young Persephone.
With the morrow, there shall be
One more wraith among your number"
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