Lol?
I was joking, but yes it is unless you're talking about a proper noun or at the beginning of the sentence?
Theres rules about when you have to capitalize words but isn't any rules against capitalizing random words, its frowned on because its hard to read sentences with all capitals, which is way lots of legal contracts are written in all capitals so you can barely read it and end up signing something without fully understanding the contract.
EDIT: I just wrote a long run on sentence meh I'm too lazy to fix it Lol