AFAIK this is not possible in restic.
There is Add --retries flag by aawsome · Pull Request #2515 · restic/restic · GitHub, but this has not been merged so far.
For your use case, also https://github.com/restic/restic/pull/3230 could be interesting (also not yet merged).
If you need an option to handle your bad connection but are not fixed on restic, you could also have a look at A restic client written in rust which supports to set the number of retries (in the config file).