on a personal note, i do not think governments invest in bitcoins secretly because it's a decentralized peer to peer transaction with no central authority and also it can affect the country's fiscal policy, business and also help to facilitate crime rates.
I agree with you on this. The blockchain is transparent and can be viewed publicly. It would be a stupid decision to secretly store btc. They can't afford such mistake it will create chaos not only to the business sector but as well to the whole economy.
What do you mean by government?
I think there is news about how private politicians are investing millions in Bitcoin. If they manage to achieve legalization of cryptocurrency, then their capital will increase significantly
I guess some are doing it individually but not collectively as a government body. For it is against the laws. I bet there are lots of politicians taking advantage of the volatility of bitcoin.