As I own some btc and have done for a while I'd like to contribute to the network some how but am not in a position to keep a PC on 24/7 to run a node..
Your bitcoins belong to you and you must keep your bitcoins safely.
Your contribution to the Bitcoin network does not relate to your bitcoins. To contribute, you can run a Bitcoin full node that does not need to run 24/7. It is perfect if you can manage your full node operation 24/7 but with less time, your full node contribution is still meaningful for the network by verifying blocks and transactions.
[Guide] How to run a Bitcoin Core full node for under 50 bucks!.