5 sentences

1. 他的脾气古怪，让人难以捉摸。

   tā de pí​qi gǔ​guài, ràng rén nán​yǐ zhuō​mō.

   He has an eccentric temperament that is hard to pin down.

   Source: Dong Chinese Dictionary

2. 他这个人办事非常滑，很难捉摸。

   tā zhèi gè rén bàn​shì fēi​cháng huá, hěn nán zhuō​mō.

   He is very slippery in his dealings and hard to pin down.

   Source: Dong Chinese Dictionary

3. 他这个人情绪反复，让人捉摸不透。

   tā zhè gè rén qíng​xù fǎn​fù, ràng rén zhuō​mō bù tòu.

   His moods are so unpredictable that he is hard to figure out.

   Source: Dong Chinese Dictionary

4. 他的脾气反复无常，让人难以捉摸。

   tā de pí​qi fǎn​fù​wú​cháng, ràng rén nán​yǐ zhuō​mō.

   His temper is fickle and unpredictable.

   Source: Dong Chinese Dictionary

5. 他的态度非常暧昧，让人难以捉摸他的真实意图。

   tā de tài​du fēi​cháng ài​mèi, ràng rén nán​yǐ zhuō​mō tā de zhēn​shí yì​tú.

   His attitude was very vague, making it difficult to discern his true intentions.

   Source: Dong Chinese Dictionary