I think

Ngram Count: 
2
Starts with letter: 
Yes
Indefinite Article: 
a
Google Ngram Count: 
33840833
Sense count: 
1
Contained in other ngrams: 
3
Hierarchy: 
Issue: 
1
Recommend ngram: 
(omit)
Description: 
What you write or say already implies what you think, so most likely you can omit "I think".