You can choose a specific internal IP address to assign to an instance when you create it.
The IP address must be a valid IP address of the subnet of the instance, and the IP address must not already be in use. The IP address remains attached to the instance until you delete the instance, which releases the IP address back into the pool. If you stop and restart the instance, the instance retains the same internal IP address.
In gcloud, run:
gcloud compute instances create [INSTANCE_NAME]
If you are using a custom subnet mode network, you must also specify the subnet using the --subnet [SUBNET] parameter.