I was actually wondering if there are any restrictions on age as to investing in Bitcoin?
As far as I know, there is no restriction for investors' ages on Bitcoin. Everyone has the right to invest in Bitcoin, whether young people or old people. If someone can buy/sell Bitcoin and has the ability to store it on the wallet, he/she can invest in Bitcoin. However, it is better to have sufficient knowledge about Bitcoin and crypto market first before someone begins to invest in Bitcoin.
I read threads where people have constantly introduced Bitcoin to their underaged children (10years below) and I really don't think it's necessary because I feel those kids still have some mental growth to do and since Bitcoin is a very volatile digital asset, I think children shouldn't be made to go through such stress.
Not everyone wants their children to invest in Bitcoin, especially for underaged children. Most people prefer to tell Bitcoin when their children have been mature enough. Even, a few people don't want to introduce Bitcoin to their children. They only tell Bitcoin if their children ask them and are interested in Bitcoin. So, you can't generalize that people introduce their children about Bitcoin investment.