they are telling me to check the tappets. Maybe they are too tight I guess.
I pulled the bike out of storage in the dead of Winter to give it some kicks. It acted as you described so I just put it away and the gremlins must have froze to death.
I'd start there. But that wouldnt explain why it suddenly 'came back to life' and why you had compression later on. Be interested to hear what its like when cold again. Could be a valve / tappet got stuck? Also, to Robert's point, I would check on fuel flooding into the engine. Might want to pull the oil filler cap to check if you smell gas in the case. If so, change oil immediately and check the fuel float & needle valve. Did you leave the petcock on?