Can I switch flights in Germany without having to go through immigration

Under pre-pandemic circumstances

If it still were January 2020 or earlier, I believe it is possible but difficult.

Frankfurt is a large enough airport to allow non-Schengen airside transit. Thus, with a valid onward boarding pass, it should be possible to follow the flight connections route upon arrival, proceed through security and straight back into the non-Schengen departure area. This requires the following to be true:

• your nationality permits you to enter Germany without requiring any visa
  (your Canadian nationality checks this box)

• you are not travelling with any luggage except hand luggage

• you are able to check in for the second leg before the first one departs and you are able to get a boarding pass for that flight.

Note that you are responsible for making the connection on your own and the second leg will not wait for you if they assume you are a no-show. Note therefore that you need to plan ample time between the two legs for it everything to work out.

If you prefer to fly with hold luggage, it is still possible but then you absolutely need to pass immigration, pick up your luggage, check it back in and proceed through security. Again, as your nationality is Canadian that would not be an issue in general, it just requires ample time.

Under pandemic circumstances

Most of the answer will be as above, however Covid spread prevention protocols add a layer of complexity.

You will need to make sure that you are able to enter Germany, otherwise the airline will not allow you to board (as you have separate tickets they cannot be certain that you will make the connection). This is on top of the requirements for entering India on the outbound leg and Canada on the inbound leg. In addition, you should consider the mandatory quarantine for 5 to 10 days for arrivals from high-incidence risk areas which India currently is.

I would fear that the mandatory quarantine will lead to problems when you try to go from one flight to another. I don't know if and where there are extra checks at the airport but I cannot rule it out either (and I would not be willing to take any chances).

The requirements for entering Germany from both Canada and India can be found on the websites of the respective German embassies. Currently, Canada is not a risk area (thus entry into Germany from Canada is possible) but India is.

There are special, more lenient rules for fully vaccinated people which are too much for me to go through right now. If you are fully vaccinated (meaning your second shot was at least 14 days ago) this trip might be more possible.

Note that the designation as a risk area, high-incidence risk area or virus variant risk area can change with only a couple of days' notice. You will run into additional problems if the risk status of India is elevated in the eyes of German authorities while you are there.

tl;dr: Possible under normal circumstances; I definitely wouldn't risk it during the pandemic.

Can I switch flights in Germany without having to go through immigration

If you have luggage, then with two separate tickets you will have to go through immigration but as a Canadian citizen that's probably the least of your problems.

Without luggage you MAY be able to avoid immigration, but that depends on a lot of details which are hard to predict especially during a Pandemic.

I'm just not sure if this is feasible.

Yes, it's feasible, but also more complicated.

You need to go through immigration, collect your bags, go through customs and enter Germany. Then go through the check in counter of the second flight, drop of your bags, get boarding pass, go through security & exit immigration and walk to your departure gate.

You will just to allow for enough time between flights. Since you self-transfer, you bear the full risk of missing the connection yourself. I would allow at least 4 hours but given the whole Corona uncertainty 6 hours may be safer. Add an extra half hour if you need to switch terminals.

You MUST meet all immigration and Corona related requirements for

1. Entering Germany from Canada
2. Entering India from Germany and potentially Canada too
3. Entering Germany from India (for a "short stay")
4. Entering Canada from Germany and potentially India too

These rules are complicated an also tend to change frequently. I suggest you study them carefully and make sure you can meet all requirements and conditions.